Joe Koenig Rock-Throwing Murder: Verdict, Sentence, and Appeal

Joseph Koenig was sentenced on June 3, 2025, to life in prison without the possibility of parole plus an additional 60 consecutive years for the rock-throwing murder of 20-year-old Alexa Bartell in Jefferson County, Colorado. District Court Judge Christopher Zenisek imposed the sentence after a jury convicted Koenig on all 19 counts, including first-degree murder with extreme indifference, for throwing a 9.3-pound landscaping rock through Bartell’s windshield on the night of April 19, 2023.¹

What Koenig Did

Koenig was 18 when he and two friends, Nicholas “Mitch” Karol-Chik and Zachary Kwak, loaded landscaping rocks from a Walmart parking lot into a black Chevrolet Silverado and drove through Jefferson and Boulder counties throwing them at passing vehicles. Over roughly 40 minutes, the trio struck at least seven cars.² Drivers described windshields shattering, glass shards to the face, and impacts that sounded “like a gunshot.”

Bartell was the last person hit that night. Around 10:45 p.m., as she drove north on Indiana Street near the Rocky Flats National Wildlife Refuge, a rock thrown by Koenig smashed through her windshield, struck her head, and exited through the back window. The rock was recovered nearly 140 feet away in a field.³ Her car left the road and crashed. A friend who had been on the phone with her heard the line go silent and used a phone-tracking app to find her at the scene, where she was pronounced dead.⁴

The three did not stop or call for help. According to Kwak, they drove back past the crash so he could photograph the wreckage as a “memento,” and on the way home Koenig and Karol-Chik agreed they were now “blood brothers” who would never speak of it.⁵ Prosecutors also showed the night of April 19 was not an isolated event. Karol-Chik told investigators he and Koenig had thrown objects at vehicles on at least ten different days beginning in February 2023.

The Verdict: Guilty on All 19 Counts

Koenig’s two-week trial ended on April 25, 2025. A jury of six men and six women deliberated about eight hours over two days before convicting him on every count charged.⁶

The 19 counts were:

One count of first-degree murder (extreme indifference)
Five counts of attempted first-degree murder
One count of attempted second-degree murder
Three counts of third-degree assault
Six counts of attempted third-degree assault
One count of reckless endangerment
Two counts of attempted reckless manslaughter

Prosecutors, led by Chief Deputy District Attorney Katharine Decker, argued Koenig acted with “extreme indifference for human life” and that throwing landscaping rocks at cars moving at highway speeds created an obvious “grave risk of death.” Karol-Chik testified he handed Koenig the rock through the truck’s cab so Koenig could throw it out the driver’s window, and that Koenig let out a “whoop” as they drove past Bartell’s car. Kwak said Koenig threw “shot put style” with his dominant left hand and that the group would “whoop and cheer” after strikes landed.⁷

The defense did not deny Koenig committed a crime but asked the jury to find reckless manslaughter, not murder, calling the conduct “thoughtless teenage behavior” and arguing it “never entered their minds that they were going to hurt, let alone kill, anybody.”⁸ Attorneys also argued Kwak, not Koenig, threw the fatal rock. Temple University psychology and neuroscience professor Laurence Steinberg testified for the defense that adolescent brains have a highly active limbic “accelerator” without a fully developed prefrontal “braking system,” and that the cheering atmosphere in the truck likely compromised the teenagers’ decision-making. On cross, Steinberg acknowledged that brain development varies by individual and that general adolescent research does not necessarily apply to a specific person.⁹ Koenig did not testify.

How the Life-Plus-60 Sentence Breaks Down

Under Colorado law, first-degree murder carries a mandatory life sentence without the possibility of parole, and Judge Zenisek imposed that term for Bartell’s killing. On top of that, he ordered ten years each on five additional felony counts and ten more years on a sixth count, all to run consecutively, adding up to 60 years stacked on the life term. The remaining counts were run concurrently with jail time already served.¹

Zenisek said that because the jury found Koenig threw the fatal rock, he was “more responsible than the others, and his sentencing needs to reflect that.”¹⁰ From the bench he called the rock throwing “vicious, deliberate, and intentional,” and said “the world needed more people like Alexa Bartell” and that “we’re all a little better for having known her.”

Inside the Sentencing Hearing

Bartell’s family and friends spoke before the sentence was announced. Her mother, Kelly Bartell, told the court the loss “shattered my soul” and that “there is no part of my life that will ever be the same.”¹ Her father, Greg Bartell, said his daughter’s dreams had “all been stolen” and said he would have chosen the death penalty if that option existed.¹¹ Her girlfriend, who had found her at the crash site, told the court, “A part of me died with her that day.” Family members described nightmares, an inability to drive on two-lane roads, and panic at oncoming headlights. A cousin said a paramedic who responded to the scene had to medically retire because of what he saw.

Against his attorneys’ advice, Koenig spoke. “Every day since she has died, it’s the first thing I think of when I wake up. And the first thing when I go to sleep,” he said. “I have no explanation for what we did that night.” He told the Bartell family he was “so, so sorry” and added, “I deserve the punishment that I get today. I hope that it takes away some small bit of the pain I’ve caused.”¹ Judge Zenisek said on the record that he believed the remorse was “genuine.”

Decker urged consecutive sentences on each felony, telling the court: “For the last two years, the focus in this courtroom has been on the Defendant and upholding his rights; his rights have been upheld, he received a fair trial and is facing a constitutional sentence. Now it is time to shift the focus to Alexa Bartell.”

What the Co-Defendants Received

Karol-Chik and Kwak both pleaded guilty in May 2024 and testified against Koenig at trial.

Karol-Chik pleaded guilty to second-degree murder, criminal attempt to commit first-degree murder for nine other drivers, and crime of violence. He was sentenced to 45 years and becomes parole-eligible after roughly 33 years and 9 months.¹²

Kwak pleaded guilty to one count of first-degree assault, one count of second-degree assault, and one count of attempted second-degree assault. He received the maximum 32-year sentence and becomes parole-eligible after about 24 years.¹³

Both testified that Koenig threw the rock that killed Bartell, though their accounts were not identical. Karol-Chik said the group threw roughly ten rocks each that night; Kwak said he threw none. Each had initially given investigators shifting versions of events before settling on Koenig as the thrower.⁷

Appeal

Defense attorneys Martin Stuart and Tom Ward said they plan to appeal.¹¹ Judge Zenisek noted during pretrial proceedings that some of his rulings, including admitting the adolescent-brain expert testimony, were shaped in part by concern that restricting the defense “could result in a likely appeal and possible retrial.”¹⁴

1
First Judicial District Attorney’s Office. Joseph Koenig Sentenced
2
9News. Rock-Throwing Trial: Koenig, Alexa Bartell Testimony
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9News. Rock-Throwing Death Sentencing
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Denver7. Man Who Threw Rock at Alexa Bartell’s Car Found Guilty of All Charges
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Fox 59. Rock-Throwing Suspect Said He and 2 Others Now “Blood Brothers,” Documents Show
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Denver Gazette. Joseph Koenig Found Guilty of First-Degree Murder in Rock-Throwing Trial
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CPR News. Rock-Throwing Trial: Guilty Verdict for Koenig
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Daily Camera. Alexa Bartell Rock-Throwing Trial Verdict: Joseph Koenig
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CPR News. Defense Expert Witness in Rock-Throwing Death Trial
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Yahoo News. Last Man Sentenced in Deadly Rock-Throwing Case
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Denver7. Joseph Koenig’s Attorneys Plan to File Appeal After Sentencing
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CBS News Colorado. Defendant Nicholas Karol-Chik Sentenced in Colorado Deadly Rock-Throwing Death
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Colorado Sun. Zachary Kwak Sentenced in Rock-Throwing Spree
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Denver Gazette. Expert on Adolescent Brain to Testify in Rock-Throwing Trial