The deputy was struck Friday afternoon as the suspect was being placed in a patrol car outside a mental health center in Mendenhall, southeast of Jackson, WJTV-TV reported.
The deputy was identified as James Blair, 77, WLBT-TV of Jackson reported. He was airlifted to a hospital, where he later died, the Clarion Ledger of Jackson reported.
Authorities said the suspect, identified as Joaquin Steven Blackwell, 22, was considered armed and dangerous. He was last seen with no shirt and wearing only white boxer shorts, WJTV reported.
Blackwell had been brought to the mental health center because family members had raised concerns about his mental health, the station reported. It was unclear how long or why Blackwell had been detained.
Authorities in nearby Hinds County were providing assistance, the Clarion Ledger reported.
This is a developing story. Check back for updates.