Lincoln police say 5-year-old Brian Maguire and his 7-year-old sister Charity found a loaded gun in an alley near their home.
Police say a neighbor spotted Brian holding the gun Friday evening and told him to put it down on the sidewalk.
Police say the children found the semi-automatic pistol on a concrete retaining wall in the alley, near 30th and Randolph Streets.
Police say the gun had been partially hidden by some vines growing there.
The children's father said he is just glad nobody got hurt.
"He didn't know any better. She didn't know any better. They thought it was just an air gun. I mean, that's dangerous enough in itself, but they've never even played with an air gun," said said Jason Franey, guardian.
"So, you know, aside from telling them if you find something your not sure about, leave it alone, leave it on the ground, don't touch it, go find an adult, I'm just really glad the neighbor lady had her eyes open and got the gun from them."
Police say the gun was not reported missing and officers haven't found a registered owner.