Gun that killed Billy the Kid goes to auction

A Colt single-action revolver with a 7.5 inch barrel is going on the auction block in Los Angeles.

It's over 140 years old.

But its real value, according to Bonhams auction house, is its story, involving one of the most notorious outlaws in U.S. history.

"This is the gun that killed Billy the Kid. It's one of the best documented antique firearms of the American West. We've estimated it at two million to three million dollars, and it's going on the auction block on August 27th at Bonhams," said Catherine Williamson, a Director with Bonhams.

Bonhams says the revolver has been on both sides of the law.

It belonged to Billy's gang before it was confiscated by a sheriff Pat Garrett.

Garrett later tracked the outlaw down to a ranch in New Mexico and shot him.

"It's a gun that was in the hands of both an outlaw and a lawman and a lawman again then used it to kill the outlaw. So to have that kind of provenance, to have that sort of very clear chain of ownership is unusual. It's a great story. People are still fascinated by it 140 years later."

Also up for auction: a double-barrel shotgun that Billy the Kid used to escape from a courthouse in New Mexico.

Bonhams says it expects a lot of interest in the revolver.

If it goes for 2 million dollars or more, it will become the most expensive American antique firearm ever sold in the U.S.