A five-year-old boy fatally shot his nine-month-old brother in his crib on Monday, according to police in Elmo, Missouri.

Nodaway County Sheriff Darren White told reporters the gun—a .22 caliber magnum revolver—was kept on a shelf built into the master bed's headboard. When the mother first called 911, she claimed the infant had been shot in the head with paintball gun, not handgun.

"A lady told me that she needed an ambulance. She said her 5-year-old son had shot her 9-month-old in the head with a paintball gun," White told KMA. "We dispatched an ambulance and law enforcement to the house. It was determined that the 9-month-old had in fact been shot in the head with a .22-caliber magnum revolver."

The baby was airlifted to a hospital, where he was pronounced dead.

Kathy Armentrout, a neighbor, told WDAF she brought the family's three surviving sons—who she says are five, three and one-and-a-half—to her house after the shooting.

"They're not very old so they have no clue what was happening, you know," she said. "They're a very good family and this was a tragedy. It's a sad deal. I just hope everybody prays for them."

[h/t Washington Post]