One of three Colorado teenagers accused of throwing large landscaping rocks toward at least seven cars allegedly took a photo of the final victim's car after hitting it "as a memento," according to court documents.

Joseph Koenig, Nicholas "Mitch" Karol-Chik and Zachary Kwak, all 18-year-old high school seniors, were arrested this week in connection to the April 19 rock-throwing spree, the Jefferson County Sheriff's Office said. The final rock-throwing incident claimed the life of 20-year-old driver Alexa Bartell. In two of the seven incidents, drivers suffered minor injuries.

After Bartell's death, Kwak said Koenig and Karol-Chik talked about being "blood brothers" and agreeing to never speak of the incident again, according to court documents. The day after Bartell was killed, they allegedly met up to discuss what happened, according to court documents.

The teens are charged with first-degree murder with extreme indifference. Additional charges are expected, authorities said.

As the three suspects made their first court appearance on Thursday, prosecutors said the community is outraged, and that the teens' reckless and irresponsible actions took away "an innocent life."

The teens, who were held on no bond, are set to return to court on May 3.

Koenig’s father was also arrested for allegedly trying to obstruct his son's arrest, the sheriff's office said.