"Joey had a profound impact on our department," Arlington police spokesman Sgt. Christopher Cook said, "and he had a profound impact on departments across the country. Training incidents changed because of the tragedy."

Among those changes: Only safety officers wearing fluorescent vests are allowed to carry loaded weapons during training exercises. They are barred from taking part in the exercises; their role is to protect the officers from any possible threats while they're vulnerable.

Police in Prattville, Ala., are constantly reminded to never bring a loaded gun to training activities since the death of officer Clinton Walker on Jan. 14, 2004.

In that case, a police officer retrieved his service weapon from the trunk of the car in which he had traveled to the training session. He forgot he was carrying a real gun and shot Walker in the abdomen.

Nine years later, the department still carries flowers to Walker's grave annually, Capt. Albert Wadsworth said. "You never get over it."

The small department, which typically trains with other agencies, still uses service weapons while training. But when bullets are required, multiple instructors supervise the loading and firing.

Guglielmi said Baltimore officials are committed to learning from last week's shooting and making reforms if necessary.

The department would not release its training protocols.

"We have demonstrated over the last several years, an exemplary training program," Guglielmi said.

The last police-on-police shooting in Baltimore also resulted in training changes. William H. Torbit was in plainclothes in 2011 when he responded to the Select Lounge to help disperse an unruly crowd.

When Torbit shot a patron who had engaged him, officers who were unaware that Torbit was a co worker returned fire and killed him.

The shooting resulted in a months-long internal investigation that yielded a 1,000-page report. The department enhanced instruction in night patrol, crowd control, commander incident management and firearms use

The shooting itself became a textbook case study for recruits preparing for frenzied situations of high stress and friendly fire scenarios.

Of all the tips, Scott said, one simple rule trumps the rest.

"Never point a weapon at an item or person unless you intend to shoot it."

Baltimore Sun reporter Justin Fen ton contributed to this article.

jgeorge@baltsun.com

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Training safely

•Notify dispatch — and local law enforcement, if necessary — of training locations.