Jefferson County Sheriff's Office
From left, Zachary Kwak, Nicholas Karol-Chik and Joseph Koenig.
CNN  — 

One of three teens accused of killing a 20-year-old Colorado woman after hurling a large rock through the windshield of her car snapped a photo “as a memento” of the crime, according to arrest affidavits released Thursday.

Alexa Bartell was killed April 19 after her vehicle and several others were struck by rocks, said Jacki Kelley, spokesperson for the Jefferson County Sheriff’s Office. Authorities believe at least seven vehicles were hit by large landscaping rocks.

The 18-year-old suspects – Joseph Koenig, Nicholas Karol-Chik and Zachary Kwak – were arrested Tuesday on charges of first-degree murder and extreme indifference, according to the sheriff’s office. They are being held without bail.

CNN has reached out to the public defender’s office to see if the three suspects have attorneys assigned to them.

After taking the photo of Bartell’s car, Koenig and Karol-Chik talked about being “blood brothers” and that “they could never speak of this incident again,” according to the affidavits, which were released Thursday, the same day the teens made their initial court appearance.

The suspects appeared via Zoom before First Judicial District Judge Mark M. Randall in Jefferson County Court. They did not enter pleas and will be in court on May 3, according to the court docket.

Jefferson County Sheriff's Office
Alexa Bartell

Karol-Chik allegedly told investigators that he felt “a hint of guilt” after seeing the victim’s car.

Karol-Chik also told police that, after striking Bartell’s car, Kwak – who allegedly threw the rock that killed the woman – said, “We have to go back and see that,” according to the affidavits.

After circling back, Karol-Chik told investigators Koenig slowed down so that Kwak could take a picture of the car. When police asked why, Kwak replied that he thought “Joseph or Mitch would want it as a memento,” according to the affidavit.

The court documents said Karol-Chik told investigators the suspects felt “excited” when the rocks hit cars.

The day after Bartell was killed, Koenig and Kwak met and “tried to get their stories straight about (what) happened, specifically denying involvement,” the affidavits said.

The night she was killed, Bartell was on the phone with a friend when the conversation ended abruptly, according to arrest affidavits.

Bartell’s friend used the Find My iPhone app to locate Bartell and found her phone in a field south of State Highway 128 in Golden, Colorado, the affidavits said.

The friend found Bartell motionless and with a significant head injury in the driver’s seat of a Chevrolet Spark, according to the documents.

The friend called Bartell’s mother before dialing 911. Police found “blood all over” the inside of the driver’s side door as well as the victim, and “a pool of blood in her lap,” the affidavits said. She was pronounced dead at the scene.

The court documents said cellphone tower data and a friend of one of the suspects helped identify the teens. The friend told investigators that Koenig participated in “destructive behavior” and liked “causing ‘chaos,’” the affidavits said.

The three suspects got together the night of April 19 to “hang out” and began “picking up landscaping rock from the edge of a parking lot” and put them in a truck’s cab, according to the the affidavits.

Karol-Chik told investigators he and Kwak “both collected rocks, and that all three of them threw rocks at moving cars,” the affidavits said.

Karol-Chik allegedly said he and Koenig “have been involved in throwing objects since at least February on ten separate days.”

CNN’s Sarah Dewberry and Rachel Webb contributed to this report.