The incident unfolded after an 84-year-old man brought the grenade to the station around 6:10 p.m. The man brought the grenade in a brown paper bag and told deputies he wanted to help a friend's widow discard it.
Deputies told the man to put the bag in the parking lot and closed the front lobby and parking lot to visitors, according to Sgt. Joe Acevedo of the Sheriff's Arson and Explosives Detail.
Bomb squad investigators rendered the old grenade safe around 7:25 p.m., and normal operations resumed.
The device was later determined to be a World War II practice grenade called a MK-11.
No one was injured. No criminal charges are pending.