Three teenagers in Colorado are in court right now, accused of killing a 20-year-old woman by throwing a landscaping rock through her car windshield. Now, investigators are testifying that the trio had been throwing rocks at moving vehicles for nearly two months before their actions allegedly resulted in the woman’s death.

The three then-18-year-old suspects – Joseph Koening, Nicholas “Mitch” Karol-Chik and Zachary Kwak – were arrested in connection to the homicide of Alexa Bartell, who died after a large rock crashed through her windshield and hit her on the head on April 19, according to Fox News. They were handcuffed a short while later. In a preliminary hearing held on October 18, a judge ruled the teens would have to face trial.

The lead investigator in the case reportedly testified during the preliminary hearing that Karol-Chik told him that the trio had thrown rocks at cars approximately 10 times between February and April. Prior to the deadly incident, Koeing and Karol-Chik allegedly threw a landscaping “statue head” at a vehicle carrying a couple and their children back in April. They admitted to “throwing rocks not just at targets but at people driving,” investigators said.

All three suspects have been charged with one count of first-degree murder, one count of extreme indifference, six counts of attempted first-degree murder, three counts of second-degree assault and three counts of attempted second-degree assault.

They went on quite a rampage in mid-April, according to Fox News:

Between 10 p.m. and 12 a.m. on April 19 and April 20, the suspects allegedly threw rocks at six different cars, injuring multiple drivers and killing Bartell. Earlier on April 19, they made plans to meet up and drove to Walmart together, where they picked up landscaping rocks from the edge of the store’s parking lot and loaded the rocks into Koenig’s pickup, according to an arrest affidavit previously obtained by Fox News Digital.

A fourth friend saw the three suspects loading the rocks into their vehicle and asked them to drive him home before they went on the alleged rampage, police said. Koenig was driving the truck when the suspects left the parking lot, the affidavit states.

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 six 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. The investigator testified on Wednesday that the suspects were driving about 80 mph at the time.

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After noticing that they had struck Bartell’s windshield, the three suspects turned back around and drove past the victim’s vehicle, which had swerved into a field, at about 50 mph to observe the damage. Kwak is accused of taking a photo of her vehicle as a “memento.”

Bartell was reportedly on the phone with her friend, Jenna Griggs, at about 10:45 p.m. that night when she suddenly stopped speaking, according to NBC News. Griggs then used Find My iPhone to locate Bartell and her car. She had “sustained significant injury to her head and was not moving,” according to an affidavit. Griggs called Bartell’s mother and then 911 before a Broomfield, Colorado police officer arrived at the scene, found no pulse and described her “as cold to the touch.”

Investigators reportedly found “biological matter” throughout the car and a large “river rock’ landscaping rock” on the side of the road stained with blood, according to NBC News.

After realizing Bartell was dead in her car, Koenig allegedly declared the group of teens “blood brothers.”