What happened the night 3 suspects went on a deadly rock-throwing spree

A landscape river rock hit Alexa Bartell's car so hard, it sounded like a "rail gun," one of the teens suspected of killing her told Jefferson County Sheriff's investigators.

Arrest records obtained by The Denver Gazette said the rock slammed into the windshield of Bartell's car, hit her in the head, and exited the back window.  It's unclear from interviews with the three suspects which suspect lobbed the fatal throw.

The arrest documents showed that at least six other cars were hit that night in a 45-minute span, injuring some victims and leaving others befuddled about what happened, even wondering if a wind storm had come through the area.

On the early evening of April 19, three Arvada teenagers loaded up the back seat of a pickup truck with landscaping material and allegedly went on a deadly rock hurtling spree — at times pretending they were Marines hitting targets in a combat zone, according to a Jefferson County Sheriff Office's arrest affidavit released on Thursday.

When another member of the group of friends, Joe Bopp, asked how many rocks the suspects were taking from a Walmart landscaping display, they answered: "As much as they could carry," the arrest records said.

That's when Bopp asked the others to take him home. 

What followed was a night of precision bombardment, requiring one of the suspects to drive and the others to throw the rocks, using "Marine terms" before a rock was thrown, the affidavit stated.

Interviews with the suspects revealed that the three teens each played a role: One drove, and the two others did the throwing from the moving truck, one of them yelling directions, such as "contact left" before a toss.

Jeffco sheriffs said seven cars were hit, injuring several drivers and killing Alexa Bartell, 20, a resident of Arvada, around 10:45 that night. 

Bopp, 20, was interviewed by Jefferson County Sheriff's investigators Tuesday and hours later, three teenagers were arrested on suspicion of first-degree murder in the death of Bartell.

Bartell died when a large, rounded landscaping rock hit her windshield the night the teens went on the rock-throwing spree, which started at West 100th and Simms at around 10 p.m. and ended around 10:45 p.m. on a lonely stretch of Indiana Street, where Bartell's yellow Chevy Spark left the road, investigators alleged in the arrest documents. 

In addition to first-degree murder, extreme indifference, 18-year-old Joseph Koenig, Nicholas "Mitch" Karol-Chik, 18, and Zachary Kwak,18, could face additional charges, such as attempted murder or assault, the Jefferson County Sheriff's Office said in a press release. 

Karol-Chik, who owned the truck that allegedly transported the boys, told investigators that he and Koenig had started throwing rocks at statues and people in February.

But he said that it was Kwak who threw the rock that smashed Bartell's windshield and struck her in the head, killing her, the arrest documents alleged. 

On the other hand, Kwak told investigators it was Joseph Koenig who threw the fatal rock, according to the affidavit.

Jeffco sheriffs said that Bartell was on the phone with a friend when her voice went silent. The friend tracked her cellphone to the remote highway and found Bartell in the driver's seat. When law enforcement arrived, they discovered Bartell in the front seat with no pulse, her "arm cold to the touch."

Bartell's front windshield had a hole in it, the back window was completely blown out, the affidavit said, and a rock with what appeared to be blood on it was found by the highway.

What followed was an intense investigation that involved an elaborate web of cellphone pings, witness interviews and even a query with a nearby Chevrolet dealership as to what kind of truck would have headlights which were seen on a surveillance video. 

Koenig and Karol-Chik were both arrested at 11 p.m. on Tuesday night, and Kwak was taken in early Wednesday morning around 2 a.m. 

Koenig's father, Mark Koenig, was also arrested on suspicion of obstruction when, according to his arrest records, JeffCo deputies knocked at the family home in Arvada and asked if Joseph was home. When Joseph came to the door, his father objected to a request to search the house. When the elder Koenig got in the way, he was pulled away, arrested and eventually released.  

The arrest document said that, after the rock hit Bartell's car, the suspects circled back around and were aware that something bad had happened. Kwak told investigators that he snapped a photo of the car where it had come to rest in case his friends "would want it as a memento."

On the way home, the three teens vowed that they would always be "blood brothers" and promised never to speak of what happened that night, the arrest affidavit said. 

All three teens appeared virtually from jail on Thursday morning, Kwak with his head bowed and hair in his face, Koenig and Karol-Chik looking straight ahead. All three wore orange clogs and jail tops, Koenig and Kwak opting to wear shorts and Karol-Chik in long orange pants. 

The virtual feed was watched by several victims, including Bartell's family. One woman who had a tissue in her hand shook her head "no" when Kwak's lawyer asked to discuss the no-bond hold. 

The Denver Gazette tried to contact several victims and witnesses of the rock-throwing spree, who could not be reached or declined interviews.

All three are being held without bond. Their next hearing is May 3. 

Thursday, Bartell's family set up a fund in her honor to go toward legal expenses, to create a student athlete endowment fund, and for a memorial dedicated to the amazing daughter "who was an intelligent, kindhearted soul, with a bright future ahead of her" and "whose life was taken too soon."

Donations are accepted via Zelle @ alexabartellmemorial@gmail.com

Donations are also accepted via Venmo @Alexa-Bartell-4.

Denver Gazette reporter Julia Cardi contributed to this article.