Mark Anthony Diaz was arrested at his home in Carlsbad around 2 p.m. Thursday, said San Diego County sheriff's Sgt. Roy Frank.

Shortly after 9 p.m. Wednesday, Diaz allegedly walked into Pacific Coast Boxing on North Santa Fe Avenue and opened fire, killing 52-year-old Hector Gil at the scene.

Peter Moreno, 56, and Ricardo Gutierrez, 21, were also wounded in the gunfire but were expected to survive, Frank said.

Both Gil and Moreno volunteered as trainers at the boxing gym, while the younger man trained there.

Authorities have not disclosed a motive for the shooting but gym owner Ari Soltani told The San Diego Union-Tribune that Diaz was recently fired as a trainer. He also said he had a restraining order requiring Diaz to stay away from the business and barring him from possessing a gun.