12-yo boy accidentally shoots cousin, 5

Queensland Police are investigating how a 12-year-old boy who accidentally shot his five-year-old cousin in the face was able to obtain a registered rifle.

Police believe the older child got the unsecured gun from a shed on a rural property in Cottonvale before accidentally shooting his relative on Tuesday afternoon.

The little boy was flown to Lady Cilento Children's Hospital where he remains in a serious but stable condition after undergoing two rounds of surgery, a hospital spokeswoman said on Friday.

"Inquiries are continuing as to how the weapon came to be unsecured and circumstances surrounding the incident," police said in a statement.

Authorities have urged firearms licence holders to be mindful of their obligations under the Weapons Act to securely store their weapons.

"They're children. It's an accident - an unfortunate one. I don't know why it's happened," the boy's grandfather Tony Calvisi told The Courier-Mail.

Mr Calvisi said the children had found the gun in a place they shouldn't have been able to get to, but "children, they find things".

"They were playing with something they were always told never to touch, and I don't know why," he said.