PHILADELPHIA -- Police in Philadelphia say a 3-year-old is in critical condition after being shot in the head by his 6-year-old brother.

Authorities say the younger boy suffered a gunshot wound to the left side of his forehead just after 3 p.m. Saturday. The two boys were on the second floor of their north Philadelphia home when the shooting happened.

The injured boy was taken to a local hospital.

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Authorities believe the 3-year old, his 6-year-old brother, along with their 12-year-old brother were at the home but no adults were there, CBS Philadelphia reports.

It's not clear where the parents were or how the children got access to a handgun in the home.

"When I heard about the little boy my heart just broke down," neighbor Marainda Stewart told CBS Philadelphia. "I just felt bad. I'm praying to god that the little boy makes it through."

People in this community say they aren't just praying for the 3-year-old shot, but his 6-year-old brother too.

"The six-year-old, who shot the three-year-old, he doesn't know any better," said Stewart. "He probably thought it was a toy. He's six!"

This shooting saddens those in the neighborhood but it also frustrates some.

"They shouldn't have had access, no way," said neighbor Helen Williams. "If they couldn't secure it in the home, then when we left they should have took it with him. No it's unbelievable and it's unacceptable."

Police say the 6-year-old and his parents are with detectives.

Officials still trying to understand how the children got access to the handgun and why they were home alone.