Colorado teens arrested in rock-throwing attacks took photos of murdered woman's car as 'memento': police

 One suspect apparently said, 'We have to go back and see that,' after striking deceased victim's vehicle

The three Colorado teenagers charged with murder in a series of rock attacks on vehicles across Jefferson and Boulder counties that left 20-year-old Alexa Bartell dead last week apparently took a photo of her damaged vehicle as a "memento."

The Jefferson County Sheriff's Office (JCSO) on Tuesday identified the three 18-year-old suspects as Joseph Koenig, Nicholas "Mitch" Karol-Chik and Zachary Kwak, all of Arvada, Colorado.

The three friends made plans to meet up over Snapchat on April 19, and after driving around town for a while, they decided to stop at Walmart and began picking up landscaping rocks from the edge of the store's parking lot and loading them into Koenig's pickup, according to an arrest affidavit obtained by Fox News Digital.

A teenage witness saw the three suspects loading the rocks before the alleged incidents, police said. Koenig was driving the truck when the suspects left the parking lot.

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The Jefferson County Sheriff's Office on Tuesday identified the three 18-year-old suspects as Zachary Kwak, Joseph Koenig and Nicholas Karol-Chik. (Jefferson County Sheriff)

That witness later told police that Koenig "frequently participates in destructive behavior" because he enjoys causing "chaos," the affidavit states.

Throughout the rest of the night, the three suspects allegedly threw rocks at five different vehicles, including Bartell's, killing the 20-year-old woman just before 11 p.m. as she was driving while talking on the phone with her friend.

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Bartell's friend told police that she was speaking with the 20-year-old on the phone when she "abruptly stopped talking."

Alexa Bartell, 20, was killed during a series of apparently random rock attacks on cars across Jefferson County, Colorado, according to the sheriff's office. (JCSO)

When the suspects struck Bartell's car, Kwak allegedly said, "We have to go back and see that," according to Karol-Chik's statements to investigators.

They circled back to find Bartell's car, at which point Kwak apparently took a photo of the damage to her windshield. Karol-Chik said he felt a "hint of guilt" at that moment.

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Karol-Chik told investigators that Kwak became "excited" when he hit a vehicle with a rock. Kwak, meanwhile, told investigators that Karol-Chik would use "Marine" terminology, such as "contact left," before hitting a vehicle to the left with a rock.

When investigators asked Kwak why he took a photo of Bartell's damaged car, he said he thought his friends would want it as a "memento," according to the affidavit.

When the suspects struck Bartell's car, Kwak allegedly said, "We have to go back and see that," according to Karol-Chik's statements to investigators. (Jefferson County Sheriff)

Bartell's friend used a phone-finder app to track Bartell's location and eventually found her stationary vehicle in a field off Indiana Street in Jefferson County.

Bartell was inside the vehicle, unmoving and with a "significant injury to her head." Bartell's friend called the 20-year-old's mother before calling 911.

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Broomfield police arrived shortly afterward and found a significant amount of blood on Bartell's car door as well as "a pool of blood in her lap."

Investigators photographed a gaping hole directly in Bartell's windshield, directly in front of the driver's seat.

Investigators photographed a gaping hole directly in Bartell's windshield, directly in front of the driver's seat. (Jefferson County Sheriff)

Authorities also saw a "visible defect" on Bartell's head and "biological matter throughout the passenger compartment of the vehicle." The rear window of her car was completely broken out, police said.

South of Bartell's destroyed vehicle, investigators located a "river rock"-style landscaping rock on the side of a roadway with red staining that tested positive for blood.

Detectives then learned that there had been a string of other incidents involving vehicles struck by rocks that night and scoured cellphone data that pinged between four cell towers around the time of the rock-throwing incidents and Bartell's death. 

Between 10 p.m. and 12 a.m. on April 19 and April 20, the suspects allegedly threw rocks at five different cars, injuring multiple drivers and killing Bartell.

Between 10 p.m. and 12 a.m. on April 19 and April 20, the suspects allegedly threw rocks at five different cars, injuring multiple drivers and killing Bartell. (Jefferson County Sheriff)

They eventually identified numbers associated with all three suspects and took them in for questioning.

At first, Karol-Chik told investigators that only Kwak collected and threw the rocks at vehicles, including Bartell's. He later admitted that he and the other two suspects all collected and threw the rocks together.

Karol-Chik and Kwak had apparently been throwing rocks and other objects, including a statue, at vehicles since February on at least 10 different occasions.

The suspects are each facing charges of first-degree murder and extreme indifference. The First Judicial District Attorney’s Office may file additional charges in the future.