Driver convicted of first-degree murder in case of Colorado teens who threw fatal rock at car

The last of three friends accused of killing a driver in Colorado by throwing a rock through the windshield of her car was convicted of first-degree murder Friday.

The teens were driving around suburban Denver in 2023, throwing rocks at passing cars, when one struck and killed 20-year-old Alexa Bartell in a crime prosecutors classified as murder.

After two of the defendants had taken plea deals, the jury found the third, Joseph Koenig, guilty at the conclusion of a two-week trial during which jurors had to wade through the shifting and competing versions of the truth offered by the defendants. Sentencing is scheduled for June 3.

Koenig, now 20, insisted that another person in the trio threw the rock that killed Bartell. But the two friends, whose agreements with prosecutors could lead to shorter prison sentences, said Koenig threw it.

Chief Deputy District Attorney Katharine Decker told jurors the damage to Bartell’s car was consistent with Koenig, who is left-handed and was driving, throwing the rock, shotput-style, out the driver’s side window at Bartell’s car as one of the friends, Nicholas Karol-Chik, testified.

Even if jurors weren’t convinced Koenig threw the rock, she had urged them to still find him guilty of first-degree murder as a conspirator with his friends, who both pleaded guilty to lesser charges.

The defense didn’t dispute that Koenig participated in the night of rock-throwing but said the third defendant, Zachary Kwak, threw the fatal rock.

His attorneys argued Koenig did not know anyone had been hurt until Bartell’s car went off the road, and that he had borderline personality disorder, which affected his impulse control and judgment.

One of Koenig’s lawyers, Martin Stuart, told jurors to instead find him guilty of manslaughter, the least serious charge he faced in Bartell’s death, because he didn’t knowingly try to kill her. Jurors also had the option of finding Koenig guilty of manslaughter as a conspirator, even if they didn’t think he threw the rock himself.

On April 19, 2023, after seeing Bartell’s car leave the road after being hit, the three friends circled back a few times to look again, according to testimony and investigators. One of them, Kwak, took a photo as a memento, but no one checked on the driver or called for help, according to their testimony.

Bartell’s body would not be discovered until her girlfriend, Jenna Griggs, who was on the phone with her that night when the call abruptly cut out, tracked her phone to the field, she testified. The only DNA found on the fatal rock was Bartell’s, making the testimony from Kwak and Karol-Chik key to the prosecution.

The friends agreed not to talk to anyone about what had happened. But Kwak, the newest one to the group, later told investigators that Koenig had thrown the fatal rock.

Karol-Chik, who said Koenig was like a “brother” to him, pointed the finger at Kwak before changing his story and saying that Koenig had thrown the rock that killed Bartell.

Karol-Chik, who was sitting in the passenger seat of the pickup as Koenig drove, testified that Koenig seemed “excited” as they drove by Bartell’s car and at one point made a “whoop” sound.

“It sounded like him celebrating,” said Karol-Chik, who admitted he had placed the fatal rock next to Koenig so he could grab it and throw it as he drove.

Koenig’s lawyers tried to cast doubt on the reliability of the other men’s accounts.

“You have no reason to believe me, but I also have no reason to protect anyone anymore,” Karol-Chik said on cross-examination.

Karol-Chik and Kwak contradicted one another on a key point. Karol-Chik said they all threw about 10 rocks each that night. Kwak said he didn’t throw any. The defense pointed out that Kwak did not say Koenig had thrown the rock until a detective told him someone had accused Kwak himself of doing it.

But in their questioning of the friends, the defense also stressed that none of the three had intended to hurt anyone.

Kwak entered into a plea deal first, pleading guilty in May 2024 to first-degree assault in Bartell’s death, acknowledging that he acted in a way that created a grave risk of death.

He also pleaded guilty to second-degree assault and attempted second-degree assault for the rocks that were thrown earlier in the night. He faces between 20 and 32 years in prison, prosecutors said.

About a week later, Karol-Chik pleaded guilty to second-degree murder and committing a crime of violence. He also pleaded guilty to attempted first-degree murder for throwing rocks at a total of nine people that night and earlier in 2023. Under his plea agreement, Karol-Chik could be sent to prison for between 35 and 72 years when he is sentenced.