BANGOR — Police Chief Mark Hathaway said Friday that he made a very serious mistake while cleaning his new duty weapon that caused him to shoot himself in the left hand. The city manager agreed and has ordered Hathaway to undergo additional gun safety training.

“I was handling the firearm and I was not focusing on what I was doing and that is unacceptable,” Hathaway said while sitting in a training room at the Bangor Police Station with his left forearm and hand wrapped in a cast. “And this is the result.”

“I want the public to know we’re not making excuses,” Hathaway said. “It was without question my fault. I made a very serious mistake.”

Hathaway declined to describe Monday’s incident in detail.

An internal investigation into the shooting was conducted by Lt. Tim Reid, who leads the detective division, and was summarized in an interoffice memo issued Friday to Hathaway from City Manager Cathy Conlow.

“While there were several mitigating factors that were involved including heat and the fact that these new weapons require that the trigger be depressed in order to be disassembled, the final analysis is that [the] injury was the result of your failure to clear the chamber prior to disassembly,” Conlow wrote.

Conlow ordered Hathaway to undergo remedial training, to include reading, classroom and firearms handling, and is requiring written documentation that he completed the program.

The memorandum states that the Attorney General’s office and the District Attorney of Penobscot County were informed of the incident and both indicated it was appropriate to handle the matter internally.

Sgt. Bob Bishop, the department’s firearms training officer, was seated beside Hathaway Friday and said the incident spurred a review of departmental safety procedures already in place.

“I would like people who use or handle firearms to think about what I did,” Hathaway said, stressing gun safety. “We do not want this to happen to anybody else.”

The city’s new police chief, a 25-year veteran on the force, had just returned from weapons training in Brewer with his new duty weapon, a .45-caliber Glock handgun, when the incident occurred. Four or five officers were in the room when the gun went off, and they quickly rendered care.

“They put me on the ground and took off their shirts to wrap up my hand to stop the bleeding,” Hathaway said.

The fire department’s ambulance crew arrived in minutes and quickly took him to Eastern Maine Medical Center, he said.

“They took good care of me,” Hathaway said of his officers and emergency responders.

“I’m thankful nobody else was injured,” he also said.

The city received a Justice Assistance Grant from the federal government last fall that provided the $10,800 needed to purchase the new weapons, which were issued to all 82 sworn officers and replaced the .45-caliber Sig Sauers previously in use.

Bishop and his staff examined the firearm and it functions properly, Hathaway said, and the team also examined the entire weapons training program.

“In the aftermath of this, we put ourselves under a microscope,” Bishop said. He said everything from what is taught in the classroom to how the range is operated to cleaning weapons was reviewed.

“Everyone in the firearms instruction [team] met and discussed this,” Bishop said. “That discussion [is] going to produce changes. We’re striving for firearms excellence because the public expects us to be flawless.”

Bishop said Monday’s incident was the third accidental gun discharge within the department in the last quarter century, none of which occurred while officers were dealing with members of the public.

“That statistic is incredible,” Bishop said.

Hathaway, who was hired as chief in April at a salary of $85,893, said if he had followed the safety rules already in place, “we wouldn’t be here today.”

“I accept the criticism I received. It was well deserved,” Hathaway said.