GOLDEN, Colo. — Three Denver-area teens cheered each other during a night of throwing rocks at cars — until one of the rocks crashed through a windshield and killed a woman, leading to a murder conviction Friday after the trio turned on one another.

Jurors found Joseph Koenig guilty of first-degree murder in the death of Alexa Bartell in 2023, after the other young men riding with him reached deals with prosecutors and testified against him.

Koenig, now 20, was also convicted of attempted murder and other less serious crimes for rocks and other objects thrown at vehicles the night Bartell was killed and in previous weeks.

Bartell’s family and friends hugged and cried in court after the verdict.

Her mother, Kelly Bartell, later said justice had been done but had mixed feelings, expressing some sympathy for Koenig and the other two young men, who were all 18 when her daughter was killed.

“It’s hard to be happy or feel satisfied that justice was served today because I feel one amazing life was lost and three others are also lost and impacted,” she said.

Jurors had to consider shifting and competing versions of the truth offered by Koenig’s former co-defendants during the two-week trial.

No one disputed that a 9 pound (4 kilogram) landscaping rock taken from a Walmart parking lot crashed through the windshield of Alexa Bartell’s windshield, instantly killing her, on April 19, 2023. Her car went off the road into a field. The issue was who threw it.

The only DNA found on the rock was Bartell’s, making the testimony from the other friends, Zachary Kwak and Nicholas Karol-Chik, key to the prosecution.

Lawyers for Koenig, now 20, said that Kwak threw the rock that killed Bartell. But the two friends — whose agreements to plead guilty to less serious charges could lead to shorter prison sentences — said Koenig threw it. Although Karol-Chik said they each threw about 10 rocks that night, Kwak testified that he didn’t throw any.