The FBI is offering $10,000 for help finding the gun of a Border Patrol agent who was slain last week in a rugged area outside San Diego.

The reward offered Wednesday is in addition to a $100,000 payment for information leading to arrest and conviction of anyone responsible for killing 30-year-old Agent Robert Rosas. His body was found in the community of Campo with several bullet wounds.

The FBI says Rosas carried a black Heckler & Koch P2000, a .40-caliber gun.

Mexican authorities have detained five men in connection with the case. They say one of them — 36-year-old Ernesto Parra Valenzuela — carried a 9 mm pistol when he was captured.