(CNN) The teenage gunman in a Uvalde, Texas, elementary school came out of a classroom closet and began firing when US Border Patrol agents entered the room more than an hour after the shooter began his rampage, a source familiar with the situation told CNN on Friday.
The agents were part of a team that fatally shot the gunman, ending an attack that left 19 fourth-graders and two adults dead Tuesday afternoon.
Before the assault on the shooter, a group of 19 law enforcement officers stood in a hallway outside the classroom and took no action as they waited for room keys and tactical equipment, a state official said at a news conference.
"The on-scene commander at that time believed that it had transitioned from an active shooter to a barricaded subject," Texas Department of Public Safety (DPS) Col. Steven McCraw said.
The gunman was killed more than an hour after he started shooting inside Robb Elementary School. Members of a specialized Border Patrol unit had entered the classroom, with one holding a shield followed by at least two others who engaged the shooter, according to a US Customs and Border Protection official.
The gunman is believed to have waited for the agents to enter the room, then kicked open the closet door and began shooting, the source said.
The agents had used a key to get into the classroom, opening the door while standing off to the side since the gunman had been shooting through the door, the source said.
The Washington Post first reported the detail on the gunman emerging from the classroom closet.
The timeline of events that were part of the law enforcement response became more clear and more disturbing to the victims' families Friday as McCraw explained the school district police chief was the incident commander who made the decision not to breach the classroom door.
Yet as officers stood in the hallway, children inside Robb Elementary School classrooms 111 and 112 in Uvalde repeatedly called 911 and pleaded for help, he said. They were in the middle of the deadliest school shooting since the 2012 Sandy Hook massacre.
"From the benefit of hindsight where I'm sitting now, of course it was not the right decision," McCraw said of the supervisor's call not to confront the shooter. "It was the wrong decision. Period. There's no excuse for that."
LATEST UPDATES ON THE UVALDE SCHOOL SHOOTING
The official who was the school district police chief, Pedro "Pete" Arredondo, officials said Friday.
Arredondo has nearly three decades of law enforcement experience, according to the school district, and was recently elected to a seat on Uvalde's city council. He previously served as a captain at a school district police department in Laredo, Texas, and in multiple roles at the Uvalde Police Department.
Arredondo has not spoken about the shooting publicly since two very brief press statements on the day of the tragedy. CNN attempted to reach him at his home on Friday, but there was no response.
In all, 80 minutes passed between when officers were first called to the school at 11:30 a.m. to when a tactical team entered locked classrooms and killed the gunman at 12:50 p.m., McCraw said. The tactical team was able to enter using keys from a janitor, he added.
Within that period, 18-year-old Salvador Ramos killed 19 children and two teachers -- marking at least the 30th shooting at a K-12 school in 2022. And while, as Texas Gov. Greg Abbott said, the massacre could have been worse, the law enforcement response suggests it could have been better.
The delayed response runs contrary to commonly taught active shooter protocol, established after the Columbine school shooting of 1999, to stop the shooter as quickly as possible and even bypass helping the injured. The revelations also help explain why officials have offered contradictory information over the past three days as to what law enforcement did in response.
"The levels of failure are just incredible, beyond belief," said Anthony Barksdale, the former acting Baltimore police commissioner.
Alfred Garza, the father of 10-year-old Amerie Jo Garza, who was killed in the attack, said he believes someone should be held accountable for the delayed response.
"They should have reacted quicker, faster," he said. "Had they done that? You know, maybe we would have a different result."
Gov. Abbott told reporters Friday he was misled by authorities the day after the shooting, and he is livid.
Abbott said he took careful notes from his briefing on Wednesday, calling what he told the public "a recitation of what people in that room told me." He added, "As everybody has learned, the information that I was given turned out, in part, to be inaccurate, and I'm absolutely livid about that."
The governor was in Uvalde for a news conference about the state response for the families of those affected by the shooting, but reporters pressed Abbott on the law enforcement response and the information given to the public about the shooting.
"My expectation is the law enforcement leaders that are leading the investigations ... they get to the bottom of every fact with absolute certainty," he said.
Abbott said the people who deserve accurate answers the most are the families whose "lives have been destroyed."
"It is inexcusable that they may have suffered from any inaccurate information whatsoever," he said.
McCraw also revealed further details about how the gunman was able to enter the school unobstructed.
The suspect, Ramos, first shot his grandmother at her home, took her truck and crashed into a ditch near the school at 11:28 a.m. He exited the vehicle with a long rifle and ammo and shot at two men across the street, missing them, McCraw said.
A schoolteacher who had propped open a locked back door a minute earlier saw the crash and gunman and went to call 911 -- leaving the door propped. That 911 call came at 11:30 a.m.
The gunman then moved toward the school parking lot and began shooting into classroom windows, McCraw said. A school resource officer, who was not on campus at the time, heard the 911 call and rushed to the school but drove past the suspect, who was hunkered down behind a vehicle, McCraw said.
The suspect then entered the school via the propped door at 11:33 a.m. and went to the adjoining classrooms 111 and 112, where he continued shooting, McCraw said.
Two minutes later, seven officers arrived to the school and approached the locked classrooms where the gunman had barricaded himself. Two of the officers were shot by the suspect from behind the door and suffered graze wounds, McCraw said.
The gunman fired 16 more rounds inside the locked classrooms between 11:37 and 11:44 a.m., and more officers continued to arrive to the hallway, McCraw said.
At about the same time, the Robb Elementary School posted on its Facebook that the school was on lockdown due to gunshots in the area. Outside the school, distraught parents soon began to arrive, desperate to know whether their kids were still alive, leading to confrontations with police trying to set up a perimeter.
Inside the school, there were as many as 19 law enforcement officers in the hallway at 12:03 p.m., yet they remained outside and waited for further tactical team and equipment, McGraw said.
That very minute, at 12:03 p.m., police received a 911 call from a girl who identified herself and whispered she's in Room 112, McCraw said. She stayed on the phone for 1 minute, 23 seconds. At 12:10 p.m. she called back and said there were multiple people dead. She called again three minutes later.
Members of the Border Patrol tactical team, known as BORTAC, arrived with shields at 12:15 p.m. There they waited.
The girl called again at 12:16 p.m. and said there were eight to nine students alive, McGraw said. Another student called 911 from Room 111 three minutes later but hung up at the urging of another student. On a 911 call at 12:21 p.m., three shots can be heard, he said.
The gunman had fired over 100 rounds in the first minutes of the shooting, but the gunfire after that was sporadic and aimed at the door, McCraw said.
"The belief was that there may not be anybody living anymore and that the subject has now tried to keep law enforcement at bay or entice them to come in to (die by) suicide," he said.
A female student called 911 at 12:36 p.m. that lasted for 21 seconds, but then called back and was told to stay on the line and remain quiet. At 12:43 p.m. and 12:47 p.m. she asked 911 to please send police now.
Finally, at 12:50 p.m., the tactical team entered the room and shot and killed the suspect.
Children who survived the shooting described what happened inside the school during the mayhem.
To survive the nightmare, Miah Cerrillo, 11, smeared her friend's blood all over herself and played dead, she told CNN.
Miah and her classmates were watching the movie "Lilo and Stitch" when teachers Eva Mireles and Irma Garcia got word of a shooter in the building. One teacher went to lock the door, but the shooter was right there -- and shot out the door's window, Miah said.
As her teacher backed into the classroom, the gunman followed. He then looked a teacher in the eye, said "Goodnight," and shot her, the girl recalled.
And then he opened fire, shooting the other teacher and many of Miah's friends. Bullets flew by her, Miah said, and fragments hit her shoulders and head. The gunman next went through a door into an adjoining classroom. Miah heard screams and more gunshots. When the firing stopped, the shooter started playing music that was "sad, like you want people to die," the girl said.
Scared he would come back to kill her and her few surviving friends, Miah put her hands into the blood of a slain friend lying next to her and smeared herself with it, she said. The girl and a friend managed to grab a dead teacher's phone and call 911 for help, she said. She told a dispatcher, "Please send help because we're in trouble."
The pair then lay down and played dead.
Another student in a different classroom, 10-year-old Jayden Perez, said when he and his classmates heard gunfire, his teacher locked the door and told them to "hide and be quiet."
Jayden said he was hiding near the storage area for backpacks during the shooting. Others in his class were under a table. The entire time, he wondered what was going to happen to them.
"It was very terrifying because I never thought that was going to happen," he told CNN. "(I'm) still sad about some of my friends that died."
He does not want to go back to school again.
"No, because after what happened. I don't want to. I don't want anything to do with another shooting or me in the school," he said. "And I know it might happen again, probably."
Outside the school, chaos and confusion reigned as distraught parents showed up and implored law enforcement to force their way in and kill the gunman. One father even asked officers to give him their gear, he said.
"I told one of the officers myself, if they didn't want to go in there, let me borrow his gun and a vest, and I'll go in there myself to handle it. And they told me no," Victor Luna told CNN. His son survived.
Instead, officers held parents behind yellow police tape, refusing to let them enter as crying and screaming echoed around them, several videos show.
Members of the US Marshals Service can be seen in one video holding back parents who pleaded to enter the school. US Marshals said in a statement they were called to the school at 11:30 a.m. and arrived about 40 minutes later from Del Rio, about 70 miles away.
The first deputy US Marshals to arrive entered the school to assist the Border Patrol tactical team already engaging with the shooter. The deputies also rendered aid to victims. Other deputies were asked to secure the perimeter around the school, but never arrested or placed anyone in handcuffs, the agency said.
"Our deputy marshals maintained order and peace in the midst of the grief-stricken community that was gathering around the school," the agency said.
Uvalde Police Chief Daniel Rodriguez issued a statement Thursday defending his officers' response to the shooting amid the growing criticism.
"It is important for our community to know that our officers responded within minutes" alongside school resource officers, he said.