The mother poured the whiskey down the bathroom sink, which agitated Diem, Jackson said.
"He started to argue with her; at one point, she says he 'poked' her in the nose," Jackson said.
Diem's mother and stepfather, 79-year-old Melvin Rowley, forced Diem into his bedroom and shut the door. But he broke down the door and hit Rowley several times in the face, according to the charges. Rowley fell to the ground, and Diem climbed on top of him and continued to strike him as his mother tried to stop him by hitting him over the head with the whisky bottle, the charges add.
Diem then took his backpack, left the house and rode away on his bicycle, Jackson said. Rowley told his wife he was fine, so she followed Diem out of the house and told a concerned neighbor to call 911.
When Rowley's wife returned to the house, she found him unconscious and not breathing. She tried to perform CPR with the help of the neighbor; police officers and medics who arrived at the house continued efforts to revive him. Rowley was flown to Utah Valley Medical Center, where he died about 1:30 a.m.
Officers found Diem about midnight near his neighborhood. He was arrested and booked into the Utah County jail.
"Strider admitted that he attacked Melvin because he was mad at his mother but acknowledged that Melvin never hit [him]," according to the charges.