Boy, 4, shoots dead his playmate, Brandon Holt, 6

A 6-year-old New Jersey boy has died from injuries sustained when he was shot in the head by his 4-year-old neighbor while they were playing outside, police said.

Brandon Holt, a student at St. Joseph’s Grade School in Toms River, died in hospital at 5 p.m. Tuesday, a day after the shooting, Police Chief Michael Mastronardy said, CNN reported.

The incident – the second accidental shooting involving children in the US this week – is likely to further fuel debate on America's gun control legislation, currently a major focus among top lawmakers.

The Star Ledger reported the pair were playing in the younger boy’s backyard Monday night when the pre-schooler went inside his house and brought out a loaded .22-caliber rifle.

More from GlobalPost: Boy, 4, shoots 6-year-old neighbor in the head

A neighbor said relatives described the boys as playing “pretend shooting” before the actual shooting.

It was not clear whether the boy pulled the gun's trigger or it accidentally discharged, Mastronardy said.

The Asbury Park Press reported that following the shooting, the boy’s mother called 911 while the boy's father secured the weapon.

“Unfortunately, it’s a tragic accident,” Mastronardy said.

“Right now, what we want to concentrate (on) is working with the family and helping them through this difficult time.”

Investigations are focusing on how the boy managed to get his hands on a loaded gun from his family house.