San Francisco Department of Parking and Traffic officers called a tow truck to remove the man's pickup truck from Sargent and Phelan streets at about 3 p.m., according to police.
"He had multiple unpaid parking tickets," police spokesman Officer Albie Esparza said.
As the tow truck was leaving with the truck, the owner arrived and began arguing with the DPT officers, and allegedly assaulted one of them, according to Esparza.
The man then allegedly made a threat that caused the tow truck driver to pull into a nearby City College of San Francisco parking lot at 50 Phelan St., police said.
"He claimed that there were explosives in the back of the truck," Esparza said.
A San Francisco police bomb squad arrived and determined that some packages found in the rear of the truck were not explosives, police said.
Police have not released the man's name.