Rock-throwing arrests: Conversation between tire shop workers led to a big break in the investigation

One of the big breaks in the investigation into the death of Alexa Bartell in Jefferson County this month came after two employees at a tire shop started talking about the murder. Those workers had ties to at least one of the three suspects who were arrested this week in the rock-throwing case. All three suspects -- Joseph Koenig, Nicholas "Mitch" Karol-Chik and Zachary Kwak -- made their first appearances in court on Thursday. 

Police say their first major break came following the discovery of Bartell's body at the scene where her car crashed on Indiana Street on April 19. Officers learned soon afterwards that two other cars had been hit with landscaping rocks like Bartell's had been. Those other cars were struck two miles up the road a few minutes before Bartell's car was hit. Investigators say someone in a dark pickup truck threw rocks at the two cars near the intersection of McCaslin Boulevard and Highway 128. A rock broke the windshield of a white Subaru and hit the driver in the shoulder. A pickup behind it was hit as well but only sustained minimal damage.

Detectives then looked up how many cellphones had pinged the nearest cell towers to both locations around the same time of the incidents. There were 11 in total, but only one cellphone traveled the same path in the same time frame that the crimes occurred. That phone number belonged to Koenig.

Following Bartell's murder, at the tire shop seen above, Joseph Bopp told a co-worker named Wyatt that he had been driving around with Koenig, Nicholas "Mitch" Karol-Chik and Zachary Kwak in Karol-Chik's truck on April 19. They stopped at a Walmart in Westminster and Bopp saw them loading river rock into the truck.

Bopp had a bad feeling and insisted the trio take him home, which they did.

Wyatt told police, who interviewed Bopp and, based on his statements, they took Karol-Chik in for questioning. At that point in the investigation Karol-Chik along with Zachary Kwak allegedly confessed to throwing the rocks at moving cars. Investigators say they believe the three suspects -- all 18-year-old's from Arvada who are seniors in high school -- ultimately damaged 7 different vehicles and caused injuries to two people and the death of Bartell.

The three suspects didn't show any emotion when they were advised of first degree murder charges on Thursday. One suspect told investigators he felt quote "a hint of guilt," according to the arrest affidavit. Another suspect was described by a friend as participating in "destructive behavior" because he liked to cause "chaos."

One of the employees of the tire shop declined an on-camera interview with CBS Colorado on Thursday but said they don't regret going to police at all.

RELATED: Alexa Bartell Memorial Fund created after rock-throwing death