Story highlights Police investigating gun's ownership, station reports

The shooting appears to be accidental, sheriff's office says

The 5-year-old found the gun lying around a bed, KCTV says

(CNN) The mother called 911 to say her 5-year-old boy shot his baby brother with a paintball gun.

But it wasn't a paintball gun. It was a .22-caliber Magnum revolver. And the 9-month-old boy didn't survive.

Authorities are trying to figure out what led to Monday's shooting in Elmo, in the northwest corner of Missouri.

"At this point foul play is not suspected, and it appears at this time that the shooting was accidental," the Nodaway County Sheriff's Office said.

Sheriff Darren White told CNN affiliate KCTV that the baby was in a playpen when his brother found the gun lying around a bed.

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