The U.S. attorney's office says Edward Costa walked away from a halfway house in Riverside County last month. He was sent there after pleading guilty last year to being a felon in possession of a firearm.
On Wednesday, Costa was indicted on six federal charges of possessing pipe bombs and one count of escaping from custody.
Six crude bombs were found scattered in Palm Springs neighborhoods last May but they didn't go off. Authorities say Costa recently had broken up with his girlfriend and one bomb was found near her home.
Authorities say DNA testing linked Costa to at least two of the bombs.