BISMARCK, N.D. (AP) — U.S. Sen. Kevin Cramer's 42-year-old son has pleaded not guilty to charges related to the events that preceded the pursuit and crash that killed a North Dakota sheriff's deputy in December, but he still hasn't entered a plea on the main homicide and fleeing charges.

Ian Cramer appeared remotely in court Monday to face allegations that he stole a family vehicle and crashed it into a Bismarck hospital's ambulance bay garage door on Dec. 6. He'll be asked to enter a plea at a later hearing on homicide, reckless endangerment, preventing arrest and drug possession charges in Mercer County. Cramer remains in jail on a $500,000 cash bond.

His attorney declined to comment Monday.

Investigators have said Ian Cramer's mother was driving him to the police department to deal with a traffic citation in early December when she became concerned enough about his “actions and comments” to take him to an emergency room. After she got out of the vehicle, he got into the driver’s seat and backed the Chevrolet Tahoe through the ambulance bay’s garage door at high speed, according to court documents.

When he was spotted later in Hazen, about 70 miles (110 kilometers) northwest of Bismarck, authorities said Cramer fled from deputies.

Cramer hit speeds of 100 mph (160 kph) and kept going even after a spiked device flattened two tires, according to court documents. More spikes were set up, and he swerved and crashed head-on into Mercer County Sheriff’s Deputy Paul Martin's squad car, launching him about 100 feet (30 meters) and killing him, authorities said.

Sen. Cramer said in a statement after the fatal crash that his son has “serious mental disorders which manifest in severe paranoia and hallucinations.”