Vidal Webb was arrested Monday after a seven-hour standoff with the San Diego Police Department SWAT team that surrounded a house where he was barricaded, officials said.
He was arrested on suspicion of attempted murder and arson with great bodily injury.
The Sheriff's Department said that Webb jumped from the second tier of the housing module to the day room floor. Deputies and medical staff, including a doctor, responded immediately, but Webb was declared dead 20 minutes later.
The jail death is under investigation by the Sheriff's Department, which runs the jail. Webb was set for arraignment Wednesday.