DENVER --

A paramedic who accidentally shot a man and then treated him, will not be charged prosecutors said Tuesday.

Police said the paramedic, Cody Bettcher, was driving his sister to a party in Fort Collins in September.

Outside the home, four drunk men started harassing Bettcher's sister. A friend in Bettcher's truck jumped out and confronted the group but one of the drunk men, David Patterson, began trying to provoke him into a fight, said District Attorney spokeswoman Linda Jensen.

When Patterson shoved Bettcher's sister, she slapped him back and Bettcher grabbed his handgun, jumped out his truck, pointing his gun up in the air, said Fort Collins police spokeswoman Rita Davis.

Bettcher said he then walked to the group, told them to step away, and was then punched in the face by Patterson, Davis said.

Bettcher punched Patterson while holding the handgun, and "the gun accidentally discharged," Davis said. Patterson was hit in the shoulder.

“He intended to hit him with the butt of the gun; the handle of the gun, when he did that the gun discharged,” Davis said.

Bettcher ordered his sister to call 911, while he grabbed his paramedic rescue bag and locked up his gun, police said. He then took the phone from his sister, told police what had happened and rendered aid, Davis said.

Patterson, 22, was transported to the Medical Center of the Rockies, where he had surgery on his shoulder and was discharged, police said.

Bettcher was arrested after the shooting. He was cooperative with investigators while Patterson was vulgar and uncooperative, Jensen said.

Colorado law allowed for a person to use physical force in for self-defense or to defend a third party. Prosecutors said Bettche was acting to defend his sister.