(CNN) Albuquerque police have detained and charged a man they say is the "primary suspect" in the killings of four Muslim men, Albuquerque Police Chief Harold Medina tweeted Tuesday.
The man has been identified as Muhammad Syed, 51, according to a police news release.
The killings took place between November 2021 and August of this year, with the latest three occurring within the span of two weeks. All of the victims were of South Asian descent.
Authorities detained Syed, then searched his home and vehicle, which ultimately led them to discover "additional evidence that further tied Syed to the murders," the release said. Police said during a news conference Tuesday that the findings included evidence that shows Syed knew the victims to some extent and that an interpersonal conflict may have led to the shootings.
Medina told reporters Tuesday the department did not want to label the shootings a hate crime or attribute the actions to a serial killer because "it would've been irresponsible for us as a police department to say that and further drive fear into a community that was already in fear."
"We still don't have any indication that either of these topics or labels would've been appropriate," Medina said.
As detectives prepared to search Syed's home in southeast Albuquerque, Syed drove from the home in a Volkswagen Jetta that detectives believe was used in at least one of the killings, the release said.
"Detectives connected those homicides using bullet casings found at the scenes," the release said. "The gun used in those shootings was discovered during the overnight search of his (Syed's) home."
Syed has been charged in connection with the killings Aftab Hussein on July 26 and Muhammad Afzaal Hussain on August 1, the release said. Medina said detectives are working with the District Attorney's Office on potential charges for the November 2021 killing of Mohammad Ahmadi and the August 5 killing of Naeem Hussain.
"This has been a tough week for our community," Medina said. "But we all pitched in to solve these crimes and protect a community that felt like it was under attack."
Bernalillo County District Attorney Raúl Torrez said Tuesday that his office and the police department plan to file the murder charges in district court.
"We are also working with our federal partners on the possibility of filing and pursuing federal charges at the same time if there is an appropriate federal statute," Torrez said.
Albuquerque Police, the Bernalillo County District Attorney's Office and the Albuquerque mayor's office did not respond to CNN requests for comment.
While police have not provided details on exactly how the killings unfolded, they have said three of the victims -- Muhammad Afzaal Hussain, 27; Aftab Hussein, 41, and Mohammad Ahmadi, 62 -- were "ambushed with no warning, fired on and killed."
Then, after community members marked a somber Friday prayer followed by a funeral for two of the victims, a fourth man -- Naeem Hussain, 25 -- was found dead, hours after attending the service. He became the third Muslim man killed in the city within two weeks and the fourth since November.
While police have not definitively said all four attacks are connected, they have said they are looking into whether that is the case. With no one in custody, police have not commented on any possible motive or whether any of the shootings are being investigated as hate crimes.
However, it is "deeply troubling" that the victims were Muslim and of similar descent, Kyle Hartsock, deputy commander of the city police department's criminal investigations division, has said.
Police have not come out with any descriptions of a suspect or suspects in the killings. They have, however, said they are seeking "a vehicle of interest," which may be connected to the four killings. The vehicle is a dark silver sedan that police say may be a Volkswagen Jetta.
But it remains unclear whom the car belongs to, or where it was in the photos released by the department. Police said the vehicle "is suspected as being used as a conveyance in recent homicides of 4 Muslim men."
"Everyone believes that that vehicle is very key to what happened in at least two of the shootings," Mayor Timothy Keller told CNN on Monday. "We also have shell casings that we're able to tie together through the national database. So that is giving us some confidence. But we may have a long way to go."
A $20,000 reward is being offered for information leading to an arrest or arrests in the killings. Authorities have also set up an online portal for residents to upload videos and images that could help investigators.
The three most recent killings claimed the lives of men from Pakistan, and the spate of shootings directed investigators' attention to an unsolved killing of an Afghan man reported in 2021.
The latest killing happened just before midnight on August 5 in the area of Truman Street and Grand Avenue. Police responded to reports of a shooting and found Naeem Hussain dead from a gunshot wound.
He had attended the funeral of two other victims that same day and expressed concern about the shootings, according to a spokesman with a mosque in Albuquerque.
On August 1, officers found Muhammad Afzaal Hussain on a sidewalk around 9:19 p.m. in the area of Cornell Street and Lead Avenue. He had been shot and died as a result of his wounds, police said.
On July 26, officers found Aftab Hussein with apparent gunshot wounds in the 400 block of Rhode Island at 10:30 p.m. He also died as a result of his wounds, according to police.
The August 1 and July 26 shootings got police looking into whether they may be connected to another killing that happened November 7. That day, officers found an Afghan man, Mohammad Ahmadi, with a gunshot wound in the parking lot behind the business he ran with his brother.
"Our homicide detectives and our investigators currently believe there is a strong possibility that the same individual committed all three of these crimes," Hartsock said last week, referring to the shootings of Muhammad Afzaal Hussain, Aftab Hussein and Mohammad Ahmadi. "While we won't go into why we think that, there's one strong commonality in all of our victims -- their race and religion.
"We are taking this very serious and we want the public's help in identifying this cowardly individual who in all three cases ambushed their victims with no warning, fired shots and killed them," Hartsock added.
The killings have put the city's Muslim community on edge, with some too afraid go to the mosque, shop for food or sit outside, according to Ahmad Assed, president of the Islamic Center of New Mexico.
Assed said he too is now among the many Muslims in New Mexico grappling with fear every day.
"I get in the car, and I'm watching every which way possible. I'm watching my side mirror. I'm looking in the back. I'm looking out for any sign of anything out of the ordinary," he said.
After hearing the news of Muhammad Afzaal Hussain's death, a Muslim mother of nine in Albuquerque told her children, "'I don't want you leaving the home after a certain hour,'" the mother, Samia Assed, told CNN on Tuesday.
"I have been vigilant outside. We watch ourselves. We don't go out. Our daily routines have changed," she said.
The city is now increasing police presence at mosques, Muslim-affiliated schools and the University of New Mexico. Gov. Michelle Lujan Grisham also announced sending additional state police to Albuquerque.
"We've got extra police patrols at every mosque during prayer time. We're delivering meals to folks afraid to come out of their homes. We're providing trauma services for folks also in their home or at their mosque for what they're going through," Keller said. "Right now these are very, very trying times for this community and our city."
Naeem Hussain migrated as a refugee from Pakistan in 2016 -- fleeing persecution as a Shia Muslim -- and had just become a US citizen last month, according to his brother-in-law, Ehsan Shahalami.
The young man, who owned a trucking business, was described as a kind, generous and hardworking person.
Muhammad Afzaal Hussain worked on the planning team for the city of Española. He had studied law and human resource management at the University of Punjab in Pakistan before receiving both master's and bachelor degrees in community and regional planning from the University of New Mexico, according to a news release from the mayor.
"Muhammad was soft-spoken and kind, and quick to laugh," Española Mayor John Ramon Vigil said. "He was well-respected and well-liked by his coworkers and members of the community."
Few details have been released about the two other victims.