Flint, Mich (CNN)—Police say a seven-year-old boy shot his four-year-old cousin Sunday night, critically injuring the child.

“As I was putting them in the house, I heard a shot,” said Dorisetta Wallace, a neighbor. “And I’m thinking it’s coming from down the block or whatever. So I started closing the blinds and I locked the door. And then I heard the son’s mom hollering for the police and I saw the lights from the police car.”

Authorities say the boy found the 20-gauge shotgun in his mother’s bedroom, while the rest of the family was in another part of the house.

Police and the Department of Human Services are still investigating.