DENVER >> Three teens accused of driving around and throwing large rocks at passing cars, one of which investigators say killed a 20-year-old woman, circled back to take a photo of her crashed car as a “memento,” according to court documents released today.

Nicholas “Mitch” Karol-Chik told investigators that Joseph Koenig slowed down so Zachary Kwak could get a photo of the car where authorities say Alexa Bartell died after being hit in the head with a rock on April 19, according to arrest affidavits for the 18-year-olds. In a hint at a possible motive, Karol-Chik said all three got excited every time they hit a car with a rock that night but acknowledged he felt “a hint of guilt” passing by Bartell’s car, according to the documents.

Kwak said he took the photo because he thought that Karol-Chik or Koenig would want to have a “memento” of what had happened, according to the affidavits. Koenig did not speak to investigators after he was arrested, they said.

All three teens appeared briefly in court for the first time today but only spoke to answer short questions from the judge about whether they could hear and understood what was happening. A telephone message left for Kwak’s lawyer was not immediately returned. A person at the law firm appointed by the court to represent Karol-Chik declined to comment. Koenig is represented by a lawyer from the public defender’s office, which does not comment on cases to the media.

The three teens were arrested at their homes in the Denver suburb of Arvada this week after being identified as suspects with the help of cellphone tower data and another friend who had been hanging out with them earlier on April 19. Joseph Bopp also offered a possible explanation for the alleged rock-throwing, telling investigators that Koenig often participates in “destructive behavior” because “he likes causing ‘chaos,’” the documents said. Bopp told sheriff’s investigators he asked to be taken home after he saw the three others taking landscaping rocks from a Walmart parking lot and loading them into Karol-Chik’s pickup truck, because he said he knew something bad was going to happen, according to the documents.

Karol-Chik told investigators with the Jefferson County Sheriff’s Office that he and Koenig had thrown rocks and even a statue at passing cars on at least 10 other days before Bartell was killed. Kwak heard about what they were doing and asked to join them on April 19, according to Karol-Chick, the documents said.

Investigators believe the teens were involved in several other similar incidents in which rocks between 4 and 6 inches (10 and 15 centimeters) in diameter and weighing 3 to 5 pounds were thrown at cars in the area the night of Bartell’s death. Two other drivers suffered minor injuries.

According to the sheriff’s office, Bartell was talking on the phone with a friend when she was hit by the rock. After the call went silent, the friend tracked Bartell’s location with a phone app and found the woman dead in her car, which had crashed into a field.