Close opened his window and yelled, "Are you going to train that f—ing dog or just yell at it?" KDVR-TV reports.
The D.A.’s Office said the victims backed down from the argument to take care of their dog, and Close allegedly began shooting. Thallas reportedly died at the scene. Her boyfriend was hit twice but survived, according to KDVR.
The gun used in the shooting allegedly belonged to a Denver Police officer. In a statement obtained by KDVR, the Denver Police Department said, "Close, a friend of a Denver Police officer, took the rifle from the officer’s home without the officer’s knowledge or permission. Upon learning his rifle was missing and that it may have been used in this homicide, the officer notified investigators that the rifle belonged to him. The rifle was not issued to the officer by the Denver Police Department."
An assault-style weapon, a Glock 17, a shotgun, and a large amount of ammunition were reportedly recovered from the scene.
According to KDVR, Close fled the scene after the shooting, but he was located and taken into custody.
On Sept. 22, the D.A.’s Office announced that a Denver jury found Close guilty of first-degree murder, attempt to commit first-degree murder, and first-degree assault. He is scheduled to be sentenced on Nov. 4.
In a statement, Denver District Attorney Beth McCann said, "I am delighted that we were able to get justice for Isabella Thallas and Darian Simon. Moreover, I am extremely proud of our prosecution team for their excellent work."