An 11-year-old boy fatally shot a 16-year-old home intruder while he was with his 4-year-old sister at their northern St. Louis County home on Hallwood Drive, according to police.

The invader, along with a partner, had allegedly approached the home twice before Thursday's shooting and finally decided to break in the house on their third attempt through the front door. Upon entering, the invader was shot in the head, St. Louis County police said in a statement, according to NBC News.

Responding to a report about gunshots being heard at the residence, police found the dead teen in the foyer and managed to catch the other person who fled.

Police are currently working to get to the bottom of the matter by trying to identify the second person's identity and figuring out a motive for the alleged home invasion.

One neighbor who was questioned by the police gave a different account of what transpired, reported CNN. According to the woman, who remains unnamed, the 16-year-old never entered the house.

"They were just arguing loud, you know, back and forth," the woman said.

"He was always was just sitting right there on the porch," she said. "He never did once go inside the house."

St. Louis County police Sgt. Brian Schellman later revealed that the gun used in the shooting belonged to the child's mother, who is now cooperating with the ongoing investigation, according to Fox's St.Louis affiliate Fox 2 Now.

"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," he said.

This shooting marks the third deadly incident involving children and guns in the St. Louis area in recent weeks. Jamyla Bolden, 9, was shot and killed on Aug. 18 while doing homework, and a 21-month-old toddler died a week later after shooting himself in the torso with a gun he found.