Dunn and his girlfriend drove off and spent the night at a hotel. Dunn was arrested a day later at his home in Satellite Beach, about 160 miles away, when police tracked his license plate.
He told detectives he had been in the process of turning himself in to a neighbor, who was in law enforcement.
"His side of the story is he felt threatened and that is the reason he took action," Schoonover said.
Dunn was described by police as a gun collector who shot at local ranges. His attorney, Robin Lemonidis, said her client "absolutely" saw someone with a shotgun in the SUV. She only said "we'll see" if Florida's "stand your ground" law would be part of her defense.
Police didn't know if Dunn had a concealed weapons permit, but said he had the gun for a "long period of time."
Lemonidis said Dunn was "devastated that anyone was harmed in this instance."
Phone calls made to his relatives were not immediately returned.
Police said they were looking into whether alcohol was a factor, but didn't know. Lemonidis said it was not.