PHOENIX » A gun owner will not be prosecuted in a case of a 3-year-old boy who killed his toddler brother with a shot to the head just as their shocked mother entered the room and witnessed the shooting.

Police reports released Thursday into the child’s death show the shooting occurred as the boys and their mother went to 78-year-old Allen Duncan Haley’s apartment in Payson to get food from his refrigerator. Haley helped the family out when they were in need.

Investigators said the child’s mother tried to keep the boys nearby as she filled up boxes of food and went to a bedroom to get her sons and bring them back into the living room. Later, the mother discovered the boys had left the room again and went to a bedroom where she saw the 3-year-old with a .40-caliber handgun.

Before the mother could say anything, the gun went off, struck the youngest boy in the head and caused him to fall to the ground. His mother came to his aid and screamed for help, but the child was later pronounced dead at a hospital.

The three unsecured handguns were hidden in the apartment but weren’t locked up. The gun used in the shooting was believed to have been covered up by a towel. Haley also had rifles and other handguns that were locked in a safe.

Prosecutors said in their statement last month announcing they weren’t bringing charges that Haley suffered from dementia or Alzheimer’s. They suggested his condition and the unannounced visit by the family played a role in not bringing a case.

"Mr. Haley, who does not have children living with him and does not provide homecare for children, is a frail, 78-year-old man who admitted that he has ‘issues’ with his memory

Police said the 3-year-old had no understanding about the shooting. An investigator wrote that he didn’t believe the boy even knew what the word "gun" meant. In the immediate aftermath of the shooting, the 3-year-old wouldn’t speak about what happened.

The Associated Press is not identifying the boys because of their age.