A Colorado teenager faces up to 72 years in prison after pleading guilty Wednesday to second-degree murder, among other charges, in connection with a rock-throwing spree that killed a 20-year-old woman last year, prosecutors said.

Nicholas “Mitch” Karol-Chik, 19, pleaded guilty to second-degree murder, criminal attempt to commit first-degree murder and crime of violence on Wednesday, according to the Colorado First Judicial District Attorney’s Office. Karol-Chik is the second of three suspects to plead guilty to a series of rock-throwing attacks between February and April 2023.

On April 19, Karol-Chik — along with Joseph Koenig and Zachary Kwak — drove around suburban Denver throwing melon-size landscaping stones at vehicles, investigators said. The teens, who were all 18 at the time, threw rocks at seven vehicles.

Three other drivers were injured by rocks that night and 20-year-old Alexa Bartell was killed after a rock crashed through her windshield, according to police.

Under a plea deal with prosecutors, Karol-Chik faces between 35 years and 72 years in prison when he is sentenced on Sept. 10. The original 15 counts against Karol-Chik were dismissed as a result of the plea.

"(Karol-Chik) knowingly engaged in conduct which created a grave risk of death, under circumstances evidencing an attitude of universal malice manifesting extreme indifference to the value of human life," the Colorado First Judicial District Attorney’s Office said in a statement.

Kwak pleaded guilty to first-degree assault, second-degree assault and criminal attempt to commit second-degree assault on May 10, according to the Colorado First Judicial District Attorney’s Office. Under his plea agreement, he could be sent to prison for between 20 and 32 years when he is sentenced on Sept. 3.

Koenig has pleaded not guilty and is being prosecuted for first-degree murder for his role in Bartell’s death. His trial is set to begin in July, according to online inmate records.

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Teens threw items at oncoming vehicles for over several months

Two of the teens had been throwing items at passing vehicles over the course of several months in 2023, according to court records.

On Feb. 25, Karol-Chik and Koenig threw a rock and concrete from a truck Koenig was driving, prosecutors said. Over a month later, Koenig threw a statue head at an oncoming driver while Karol-Chik was driving.

On April 19, investigators said Karol-Chik, Koenig, and Kwak loaded up the bed of a pickup truck with large landscaping stones and began hurling them at oncoming moving vehicles as they sped around a suburban area at up to 75 mph. The teens also used military or gaming terms to coordinate their attacks.

They caused damage to all seven vehicles they struck while injuring three drivers and killing Bartell, who was wounded in the head, according to prosecutors. Karol-Chik, who was in the front passenger’s seat, gave Koenig, who was driving, the rock that hit Bartell.

The series of attacks all took place within a few miles of one another and within about 45 minutes, authorities said at the time.

Investigators said they used cellphone tracking and DNA evidence to link the three teens to Bartell's death. As authorities searched for suspects, a reward for information climbed to $17,000.

Following the teens' arrests in late April, police said one of the men took pictures of Bartell's damaged car as a memento and that they did not attempt to help her when her vehicle veered off the road.

"Mitch again stated it was Zach who threw the 'fatal' rock at Alexis' vehicle. When they turned around to see Alexis' vehicle, they drove past it northbound, and turned around southbound. Joe slowed the vehicle so that Zach could take a photo of it,'" an investigator wrote in court documents. "As they passed where the vehicle had stopped, Zachary used his cellphone to take a picture of the vehicle. When asked why, he replied that he thought Joseph or Mitch would want it as a memento."

Contributing: Saleen Martin and Trevor Hughes, USA TODAY