Jefferson County jurors on Friday found Joseph Koenig guilty of first-degree murder in the killing of Alexa Bartell after he and two other teenagers hurled a 9-pound rock through her windshield during a spree of similar attacks two years ago.
Koenig, 20, was also convicted of six counts of attempted murder, three counts of assault, six counts of attempted assault, two counts of attempted reckless manslaughter and reckless endangerment.
He will be sentenced to life in prison on June 3.
Koenig threw the large rock into the windshield of an oncoming car on April 19, 2023, killing the driver, 20-year-old Bartell. The fatal attack on Indiana Street near the Rocky Flats National Wildlife Refuge was one of several times Koenig and two other teenagers threw rocks at cars that night. All three men were 18 at the time.
“This has been, obviously, the hardest two years ever, and we got justice today,” Kelly Bartell, Alexa’s mother, . “And I don’t know how to feel about it. I’m happy. It doesn’t bring Alexa back, and that’s horrible. But we don’t ever want this to happen again to anybody else. And that has been our main goal, to make sure justice is served.”
Koenig’s attorneys presented his actions during the 2023 rock-throwing spree as thoughtless teenage behavior, rather than first-degree murder. They admitted he was responsible for Bartell’s death, but argued he should be found guilty of the lesser charge of manslaughter.
“What I’m asking you to do, folks, is to go back and talk about all the evidence we heard, all the evidence we saw and return verdicts of guilty of manslaughter and attempted manslaughter — because that is what Joe Koenig did,” defense attorney Martin Stuart told jurors during closing arguments Thursday.
Defense attorney Tom Ward declined to comment after Friday’s verdict.
Prosecutors focused on how often the teenagers threw rocks at cars during the spree and how they encouraged each other by cheering when the rocks hit cars. The driver of the truck sped up before the attacks, witnesses testified, and Koenig whooped with excitement after Bartell was killed and her car drifted off the road.
“He did this over and over and over and over and over and over and over and over and over, until Alexa Bartell’s life was over,” prosecutor Katharine Decker told jurors during closing arguments.
The defense presented evidence about how teenagers are developmentally different from adults and evidence that Koenig had been diagnosed with mental conditions that impaired his decision-making at the time of the attacks. The three teenagers didn’t think through their actions, Stuart said.
“One thing they were consistent about, from start to finish, is that it never entered their minds that they were going to hurt, let alone kill, anybody,” Stuart said.
Koenig was joined in the truck during the 2023 spree by two others, Nicholas “Mitch” Karol-Chik and Zachary Kwak. Both of those men pleaded guilty and agreed to testify against Koenig during his jury trial.
Koenig’s defense attorneys argued that he did not throw the fatal rock, and that Kwak actually threw it. Prosecutors maintained that Koenig threw the rock that killed Bartell. Both sides acknowledged that, legally, all of the teens could be convicted in Bartell’s killing regardless of who threw the rock.
“We don’t have to prove he threw this rock that killed Alexa Bartell,” Decker said. “…The defendant was at least complicit in all of the crimes.”
After the verdict, First Judicial District Attorney Alexis King thanked investigators for their work.
“Regardless of this verdict, it does not bring Alexa back,” King said. “Despite a conviction of murder in the first degree – extreme indifference, none of this ever had to happen.”
Karol-Chik pleaded guilty to second-degree murder and attempted first-degree murder in 2024 and faces between 35 and 72 years in prison. Kwak pleaded guilty to assault and attempted assault and faces between 20 and 32 years in prison.
Their deals were contingent on their testimony, so neither Karol-Chik nor Kwak has been sentenced. They will be sentenced in early May.
