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An 11-year-old St. Louis-area boy fatally shot a 16-year-old who entered his home during an alleged home invasion Thursday, police said.

The shooting happened on Hallwood Drive in northern St. Louis County at around 2:20 p.m. local time (3:20 p.m. ET), police said.

Two people had approached the home twice before Thursday, and on the third attempt entered the house through the front door, police said. The 11-year-old who lives in the home shot the 16-year-old intruder in the head, St. Louis County police said in a statement.

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Police found the shot teenager dead in the foyer, and a second person who fled was caught nearby.

Police were working to verify the second person’s identity Thursday afternoon. The names of those involved, and a possible motive in the suspected home invasion, were not released.

Police said the 11-year-old and a 4-year-old girl who was also inside the home were not injured. Their mother, who was not home at the time of the shooting, is cooperating with the investigation, police said.

The gun belonged to the 11-year-old's mother, St. Louis County police Sgt. Brian Schellman told NBC station KSDK.

"Initial statements the mother made to our detectives is that she purchased it because her home has been the target of several burglaries over the past few years, and she purchased it for self-protection," Schellman said.

Schellman said Thursday's shooting was the latest instance of a child using a gun with deadly consequences. He referenced last week's deadly accident in which a 21-month-old toddler in another part of the county found a loaded handgun and shot himself. The child later died at a hospital.

"Children have access to guns all too often, and all too often they end in tragic circumstances," Schellman said.