A Richland County, SC, sheriff's deputy killed himself using his service weapon in his cruiser while on duty Friday afternoon, Sheriff Leon Lott announced Monday.

Senior Deputy Derek Fish, 28, shot himself with his department-issued gun in his patrol car Friday, Lott said. After finishing his shift, the deputy drove his patrol car back to Region 3 headquarters on Bishop Avenue and parked behind the building, where he is believed to have shot himself between 6:30 and 8 p.m. Another deputy found him.

"We're all struggling to try to understand why, and we don't have an answer," Lott said at a Monday news conference to discuss Fish's death and suicide prevention, a move approved by the deputy's family. "He didn't leave a note, he didn't communicate with anybody what his intentions were. For all purposes, that shift was a normal shift."

Fish, who was known as "Nemo" in the department, joined the agency in May 2011, Lott said. He worked his way up the ranks and was promoted last week to master deputy.

Lott said Fish, who was known for his energetic personality and smile, had not dealt with any major or traumatic events recently.