ST. AUGUSTINE, Fla. -

A 40-year-old man was shot to death Sunday after an argument that started in the parking lot of a library on Ponce de Leon Boulevard in St. Augustine, police said.

Outside the St. Johns County Public Library, David Blythe, 40, and his girlfriend got into an argument, detectives said. They said he hopped into his car and did reverse doughnuts in the parking lot. Police said he then jumped out of the car and ran down the road on U.S. Highway 1.

Detectives said Blythe tried to hop in another pickup truck, filled with a beach-bound family of four, including two children. Officer Mark Samson, of the St. Augustine Police Department, said the driver ran into the house to get his father, and a gun.

"As they come outside, they see him halfway outside the driver's door of the truck, trying to get the keys in the truck and the girlfriend's saying, 'No, you can't have anything. I've got kids here,' and at that point she feels he tried to take one of the kids out of the truck," Samson said.

The pickup truck driver's father came around the truck and got into a physical altercation with Blythe, Samson said.

"And he is being choked to the ground, almost unconscious by the way the story's being relayed to me," Samson said.

Then, the shooter told police he pulled the trigger, firing a single bullet into Blythe's head, ending a few minutes of pure chaos.

Those involved in the shooting told Channel 4 they're doing OK, but just want some privacy. Close friends of Blythe said his family is in mourning and what happened is something they never would have expected out of him.

Police detained the shooter but said he was being cooperative and didn't appear to have done anything wrong. He has been released.