A Glendale police officer has resigned after an internal investigation found he improperly used force on an unarmed suspect by striking him repeatedly on the head with his Taser, officials said Wednesday.

An internal report provided by the department says officer Joshua Carroll also had five previous disciplinary action against him between 2016 and January of this year before the latest incident, which took place in June.

"Officer Carroll has a pattern of discipline involving poor decision making that has escalated to a point that I no longer have confidence in his ability during routine contacts and stressful situations,'' wrote a Glendale police commander, in a memo to an assistant police chief.

"He has demonstrated an inability to maintain composure and appropriate officer presence, and to respond appropriately to the situations with which he is faced,'' the memo said. "These poor decisions have occurred while he is on and off duty and he has violated multiple policies. These decisions have put our Department, other officers and our community at risk."

A review panel voted that Carroll did not respond properly when he used his Taser to repeatedly strike the suspect, identified as David Dulaney, on June 13 after he approached Dulaney as he was sitting behind the wheel of his parked car.

Department officials on Wednesday released video of the incident recorded by Carroll's police body camera.

Carroll responded after a passerby reported the man looked like he might be in distress or sleeping. Carroll approached Dulaney, who told him he was waiting for a friend.

As the conversation continues, the video shows, Dulaney reaches inside and opens the vehicle door, but repeatedly tells Dulaney to stay inside the vehicle as the man starts to exit, appearing confused.

Carroll then engages in a struggle and begins using his stun device on the man, then pulls him from the car where he continues doing so, driving the device into the man's back as he attempts to handcuff him. Carroll also can be seen repeatedly striking the back of the man's head with his stun device while the man is on the ground, eventually opening a wound.

In an interview with investigators who reviewed the incident, Dulaney said he had suffered a head injury 18 years ago when he fell off a ladder, a report indicates. It adds the man appears mentally disabled as a result of the injury, but the man recalled the incident with Carroll the prior day.

"He was hitting me on the back of the head with something, I don’t know what it was,' the report quotes Dulaney as saying. "It wasn’t his hand, I know it wasn’t his hand, there’s no way it felt like-like that but he was hitting me in the back of the head, it was hurting my head, face and pushing me into the stones that were really really hot. I said why are you doing this? Why are you doing this? Please stop. Please stop."

Carroll, in his interview with internal investigators, said he thought Dulaney was reaching for a weapon from the car. He admitted using his Taser to "pistol whip'' the man because he was resisting and Carroll was frightened.

"The more he fought me with one cuffed arm, um, it just added to that level of just full-on terror on my end,'' Carroll is quoted as saying in the report.

According to police, Carroll's list of previous discipline included an incident in January during a pursuit in which he advised a police trainee to exceed 100 mph and run red lights. Carroll also fired a round from a rifle at a suspect in that same incident, police said. He was given a written reprimand.

He also was found at fault in a 2018 traffic collision, for which he received a memo of correction. Carroll was given a letter of counsel in 2018 for an improper post on Facebook and also that year given another memo of correction for misrepresentations on his resume during a department promotion process.

In 2016, he received a memo of correction for three AVL (automated vehicle locator) violations, police said.

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