WELD COUNTY, Colo — A deputy who was in training has been fired and charged with assault after video shows him punching a suspect in the back of the head while trying to restrain that person. 

Two other deputies have also either been fired or resigned following the incident, the Weld County Sheriff's Office said. 

The Sheriff's Office said the suspect was being held on Oct. 18 in one of its interview rooms.

Deputies were attempting to restrain the suspect, and the Sheriff's Office said the suspect was resisting and refusing to follow commands. At some point during this process Deputy Paul Sanders, who was in training at the time, punched the suspect in the back of the head, according to the Sheriff's Office. 

Raw video of the incident:

Weld County Sheriff explains the incident:

The Sheriff's Office said that punching is not instructed or approved by its department. 

The incident was reported that day, and the Sheriff's Office said an internal investigation was immediately launched. 

Sanders was issued a summons for 3rd-degree assault and fired. 

Deputy Todd Deutsch, who was also involved in the incident, resigned from his position. Sergeant Scott Holmen was fired based on the results of the investigation, the Sheriff's Office said. Both Deutsch and Holmen had been with the department for 15 years. 

SUGGESTED VIDEOS | Local stories from 9NEWS