When her service weapon is not on her, city homicide detective Peg Sherwood keeps it in a safe, stored in a closet and locked with a key. Her husband, Teddy Anderson, a sniper on the SWAT team, also keeps his guns locked and out of the reach of their 7-year-old son.

"We made him aware of our guns, and let him touch them," Ms. Sherwood said. "We figured that would take the curiosity away."

Keeping guns safely secured while off duty is a concern for police officers, especially those with children. Still, many local police agencies have only vague policies on weapon storage at home, leaving it up to officers to store their guns for easy access yet out of the reach of children.

Though accidental shootings involving the children of police are rare in Western Pennsylvania, a pair of dismaying cases in as many months shows that even among professionals, keeping weapons safe but accessible isn't always simple.

Port Vue police Officer John Thompson's 4-year-old son, Gavin, was able to retrieve his father's .45-caliber service weapon from the top shelf of a bedroom closet on Nov. 26 at their home in Liberty. It discharged, killing the boy, in a case still being probed by Allegheny County homicide detectives.

In October, state Trooper Nicholas Petrosky's son, also 4, accidentally wounded himself with his father's personal gun at their home in Donora. Washington County District Attorney Steven Toprani wouldn't say how the boy got hold of the gun or where it was kept, only that his review of the case remains open.

Though every officer's living situation is different, "as a general rule, if it's not on the officer's person where he can control what is done with it, it needs to be under lock and key of some sort," said Michael Lesnick, a former federal police officer whose 3-year-old son, Joshua, accidentally killed himself three years ago with a pistol he found in his father's nightstand. He pleaded no contest to charges of keeping a loaded firearm near a child and served a year of probation before he started sharing his story with other gun owners, namely police. Officers are familiar and comfortable with guns, he said, and can become complacent with safety precautions.

"To some degree, I've lost my livelihood," said Mr. Lesnick who lives in Wisconsin and is no longer in law enforcement. "My wife, who was home at the time and saw our son die, she suffers greatly from post-traumatic stress and nightmares. I carry a lot of guilt because, the bottom line, is this is my fault because if anyone knew better, it was me. Not only was I a cop, I was a firearms instructor. I used to stand up in front of people and say, 'don't do this.' To add insult to injury, I went through the criminal justice system on the wrong side. The only way you can describe it in one word is devastating."

Mr. Lesnick, who worked as a federal officer in northern Illinois for almost six years, also spends his days tracking news stories of other accidental shootings, which he prints and catalogs. To his knowledge, Mr. Thompson's case was the fourth or fifth fatal incident involving a police officer this year, though statistics on accidental shootings by the children of police officers are hard to come by.

The Centers for Disease Control and Prevention found that 138 children and teens were killed accidently by guns in 2007, and 3,588 were shot accidentally but survived in 2009. But the data isn't broken down to show cases involving law enforcement.

Many local police agencies suggest ways, but do not expressly mandate, how an officer should secure a service weapon while off-duty or at home. The state police doesn't have a specific regulation regarding the issue, though "the use or handling of firearms by members in a careless or imprudent manner or unjustified endangering of human lives by firearms in violation of the rules and regulations relating thereto, is strictly forbidden."

"Troopers generally are urged to use common sense in dealing with their weapons," state police spokesman Jack Lewis added.

For Pittsburgh police, "firearms should be stored in such a manner as to prevent access to untrained or unauthorized persons." The bureau's police policies and procedures states that "officers shall secure their firearms at all times in such a manner as to restrict irresponsible use," but does not elaborate.

The issue has been a topic of discussion during police recruit training for the past 10 years, Deputy Chief Paul Donaldson said.

"We cover different methods of storage, types of locks and the pros and cons of each system or method," he said. "Handouts are included as a reference where these things can be purchased."

The International Chiefs of Police Association, too, advises officers use trigger locks, safes or gun lock boxes when they can't keep duty weapons on their person. It makes no mention of whether guns should be stored loaded or whether ammunition should be stashed separately.

Best practices are hard to establish because living situations differ from officer to officer and weapons storage is a "very individual thing," said Betsy Branter Smith, a recently retired Naperville, Ill., police sergeant who manages a law enforcement training company and has written about the issue of gun safety for police publications.

"It's a fine line officers walk between keeping themselves safe, keeping their families safe, and we have a moral obligation, even when we're off-duty, to keep the community safe," she said. "What we don't want police officers to do is not to bring that gun home or not have a firearm available because they're too afraid of having guns in their house."

She said officers and civilian gun owners alike should familiarize their families and children with guns so they understand their dangers whether they're at home or elsewhere.

"Guns are like Christmas presents, you can't hide them from kids," Ms. Smith said. "Familiarity is what makes a kid safe."