Luis Ricardo Hernandez, 26, is accused of killing Christopher Soriano, 36, Monday, in the parking garage of the apartment complex where Hernandez is employed.
Santa Clara County, Calif. court documents say Hernandez was asked by his supervisor, Salvador Orozco Saldana, to help in a citizen's arrest of Soriano, whom Saldana suspected of recent apartment break-ins.
Soriano and Hernandez attempted to subdue Soriano, who broke free, and Hernandez shot Soriano with a gun he later said he illegally purchased for self-defense, police said.
An autopsy on Soriano indicated he had been shot at close range and was either crouching or lying on the ground when he was struck, the Santa Clara County medical examiner's office said.
Saldana wasn't charged with a crime, the San Francisco Chronicle reported Friday.