Raulie Casteel thought drivers along Michigan's Interstate 96 were part of a government conspiracy against him, he said in court Monday.
So he started firing.
Casteel, a husband and father, is taking the stand in his own trial, which continues Tuesday.
"To my way of thinking at the time, [the shooting] was to get rid of the demons so to speak. It was those thoughts – the fear, the anxiety," the confessed shooter said Monday.
Casteel, 44, is charged with terrorism, assault with intent to murder and firearms charges for the October 2012 shootings.
During two hours of testimony Monday, he said he never intended to terrorize or kill anyone.
After being fired from his job as a scientist, Casteel says he believed his phone calls were being monitored – and that government helicopters were watching him.
"They would hover above the rooftop in what seemed like an attack on the house," Casteel said.
Miraculously, in the 23 shootings, only one person was hurt. That victim limped into a gas station for help.
Another driver, Jennifer Kupiec, says the bullet missed her by a millisecond – and that Casteel was laughing when he shot at her car.
"I started to cry hysterically. I could see right away where the bullet was. I know that could have been me," Kupiec said.
He has pleaded not guilty to the terrorism and assault charges. If convicted, he could face life in prison.