Colorado Teen Pleads Guilty in Deadly Rock-Throwing Spree

A 19-year-old Colorado teen has been found guilty of his role in a series of seemingly random rock-throwing attacks that resulted in the death of a 20-year-old woman last year. The teen, Zachary Kwak, admitted to his involvement in the spree and pleaded guilty to charges of first-degree assault, second-degree assault, and criminal attempt to commit assault.

A 19-year-old Colorado teen has pleaded guilty for his role in a deadly rock-throwing spree with his pals that killed a 20-year-old woman in Denver last year.

Zachary Kwak, of Arvada, pleaded guilty on Friday to one count of first-degree assault, one count of second-degree assault and an added count of criminal attempt to commit assault, Fox 31 reports.

He was previously charged with murder but pleaded guilty as part of a plea deal and will serve no less than 20 years but no more than 32 years. He will be sentenced on Sept. 3

Prosecutors say that Kwak, along with Joseph Koenig and Nicholas "Mitch" Karol-Chik, threw rocks at six cars and injured multiple drivers after 10 p.m. on April 19. They were all 18 at the time.

Earlier on April 19, they made plans to meet up and drove to Walmart together, where they picked up landscaping rocks from the edge of the store's parking lot and loaded the rocks into Koenig's pickup, according to an arrest affidavit previously obtained by Fox News Digital.

Throughout the rest of the night, the three suspects allegedly threw rocks at six different vehicles, including Bartell's, killing the 20-year-old woman just before 11 p.m. as she was driving while talking on the phone with her friend. The investigator testified on Wednesday that the suspects were driving about 80 mph at the time.

Bartell's friend told police that she was speaking with Bartell on the phone when she "abruptly stopped talking." She was driving on the 10600 block of Indiana Street at the time, according to the Jefferson County Sheriff's Office (JCSO).

After noticing that they had struck Bartell's windshield, the three suspects turned back around and drove past the victim's vehicle, which had swerved into a field, at about 50 mph to observe the damage. Kwak is accused of taking a photo of her vehicle as a "memento."

Investigators used cellphone data to identify the suspects, tying a common phone number that pinged at different crime scenes.

The Jefferson County Sheriff's deputy also testified that, based on his interviews with the suspects, Kwak and Koenig were the only two suspects accused of throwing the rock that killed Bartell.

Investigators photographed a gaping hole directly in Bartell's windshield, directly in front of the driver's seat. (Jefferson County Sheriff)

After investigators interviewed Kwak, he allegedly insisted that he did not throw the rock that killed Bartell. When the detective who testified Wednesday told Kwak, "I hear you," he responded: "I don't need you to hear me. I need you to believe me. I did not throw that rock."

Bartell's family was in the courtroom on Friday to hear Kwak make his guilty plea. They could be seen wiping tears from their faces during the 15-minute proceedings, FOX 31 reports. They offered no comment while leaving the courthouse.

Kwak was dressed in a jail uniform, handcuffed. He answered the judge's questions, saying he understood his plea and its implications.

Investigators previously said that the trio had been throwing rocks at moving vehicles for about two months before their actions allegedly resulted in a fatality.

Koenig and Karol-Chik's cases are ongoing. All three were initially charged with murder in the first-degree with extreme indifference.