How might an officer show signs of posttraumatic stress disorder?

Increased irritability, dissociation causing changes in character or behavior and even possibly induce reckless driving , lack of sleep due nightmares, an officer might be triggered by loud noises or flashing lights that might reference past issues with guns that involved an ambulance or police car

On edge and if gun shots went off he would probably fire back without thinking ahead

Good samaritan law protects civilians when they render aid to someone in need.