Co-defendant testifies in deadly Colorado rock throwing attack

A co-defendant in a deadly rock-throwing attack in Colorado two years ago took the stand Thursday to testify against his friend, Joseph Koenig.

Nicholas "Mitch" James Karol-Chik and Zachary Kwak pleaded guilty last year to their involvement in the death of Alexa Bartell, who was killed when a rock was thrown into the windshield of her moving car in April 2023 in Jefferson County. Authorities said several others were injured in similar incidents when "large landscaping rocks," concrete and a statue were thrown at vehicles.

As part of their plea agreement, Karol-Chik and Kwak agreed to testify against their friend and co-defendant Koenig.

In July 2024, the judge delayed Koenig's trial to allow for a mental health evaluation after the defense raised concerns over an ADHD diagnosis. He is facing charges of first-degree murder with extreme indifference and several counts of attempted murder and assault after allegedly throwing rocks at other vehicles.

Koenig's defense maintains that he did not intentionally kill Bartell and claims that the other two have changed their version of events on who threw the rock. However, prosecutor Katharine Decker said Karol-Chik and Kwak's testimony will point to Koenig as the one who threw the rock that killed Bartell.

Kwak took the stand Thursday afternoon, stating Koenig contacted him on Snapchat the night of April 19, 2023, asking him to hang out. Shortly after, he said Koenig and Karol-Chik picked him up from his home in a black Chevy Silverado belonging to Karol-Chik. Karol-Chik and Koenig were longtime friends, said Kwak. He had met them only a few weeks before April 19.

Kwak said he sat in the back seat of the pickup as they rode around that night. He admitted under oath that when they stopped at a Walmart, he shoplifted some Starburst. It was at Walmart, he explained, that they began taking landscaping rocks and placing them in the truck. Some went in the footwell in front, others the footwell in back. Kwak said he was sitting behind the passenger seat, and there were bottles and a toolbox that occupied the seat and floor behind Koenig in the driver's seat.

They had already taken another friend home who did not want to be with them that night. Kwak said he, too, opted out. "I didn't want to be a part of what was about to happen." He told the court that he was told they would not take him home.

Kwak said that he did nothing to stop the rock throwing that was being done only by Koenig and Karol-Chik.

"I shut up and didn't stop it. I seen these things happening and I did not think deeply into the repercussions of these actions and I did not, did not, stop anything," he said.

He testified that he could see the digital speedometer reach 103 miles an hour as Koenig sped up while they approached Alexa Bartell's approaching car on Indiana Street. He felt the cold air and said the roar of the wind through the open window made hearing anything else difficult.

"I remember seeing headlights coming up. And I remember them being kind of just a blur. And I remember looking down and hearing a noise. Very, very loud noise," Kwak said. He claimed that he saw Koenig eject the rock like a shot put throw.

After Bartell's car was hit, he said he turned around in the back seat, "And all I could see was the black road, the black sky and bright red taillights." He watched as Bartell's vehicle drove off into the field.

He said the trio then turned around and went back for a look. From a distance, he took a picture with his phone to show the others, which, due to darkness, he said came out blurred. He deleted it, and investigators were unable to recover the photo. Kwak admitted they did not check on the driver, telling the court they didn't because of "the whole childish fear of getting in trouble, I think."

Koenig, he said, shared that he had seen glass and blood on the road.

They pulled away, drove up the road, then turned around and went back for yet another look, Kwak explained. The car remained off in the field.

Kwak said he didn't think there was something wrong, but felt it. "It's an unbelievably queer experience, but it's something that you feel. I felt it. I don't know what it is." He was troubled. "I was flipping out in my skin, and I couldn't figure out why they weren't."

Soon, there was discussion about a cover-up, Kwak testified.

"I remember hearing Mr. Koenig saying that something about this makes us blood brothers or something, and we can never talk about this," he shared.

The following day, Kwak said he met with Koenig at a Denny's. "He told me not to say anything. Joe said he looked it up, and there was a fifty-fifty shot we were caught. Or you know, if none of us talk, none of us are going to get in trouble."

Six days after the incident, Kwak was taken into custody. At first, he denied knowledge, but then, after a detective told Kwak the blame was being placed on him for throwing the rock, that changed. He told the investigator that Koenig threw the fatal rock.

Under cross-examination, defense attorney Tom Ward accused Kwak of placing the large rock in the truck when they were gathering them despite Karol-Chik's objection.

"And when you put that rock in the car, Mitch said to you, 'No, not that one, that's too big,'" said Ward. "I don't recall that," said Kwak in return. "He said that one's too big and he threw it back out of the truck and you said, 'If you won't throw it, I will,'" Ward continued. "I do not recall that," answered Kwak.

Ward noted that in the days after the incident, Kwak attended his prom and also went snowboarding.  

After Kwak, prosecutors are expected to call Karol-Chik to the stand to testify as well. He, too, got a plea deal and is expected to point the finger at Koenig as the one who threw the fatal rock. That could come Friday.