BRADENTON, Fla. -- Just one day after a celebration for its 69th birthday, Bradenton’s most famous manatee has died.

The South Florida Museum posted to their Facebook page Sunday that Snooty’s death was a ‘heartbreaking accident’ and that it’s being investigated.

"Our initial investigation indicates that Snooty's death was a heartbreaking accident and we're all quite devastated about his passing," said Brynne Anne Besio, the Museum's CEO. "We're reviewing what happened and will be conducting a full investigation into the circumstances."

Snooty was found Sunday in an underwater area only used to access plumbing for the exhibit life support system. The door is normally bolted shut, but somehow was knocked loose and Snooty was able to swim in.

“This morning, aquarium staff came in at 8am as usual and were not able to locate all of the manatees in the tank, which is the first thing they do,” said Jeff Rogers, provost and COO for the South Florida Museum. “A quick assessment showed that an underwater hatch used to access plumbing associated with the life-support system was somehow knocked loose and was open. The manatees had access to get into this tight area. The young manatees were able to get in and out. It appears Snooty was able to get into the area but was not able to retract himself from that situation.”

Museum officials say Snooty's habitat goes through daily inspections and nothing out of the ordinary was noticed on Saturday.

Snooty had been the oldest known living manatee in captivity. The museum says the other rehab manatees – Randall, Gale and Baca – are all fine.

Snooty was born in Miami in 1948. His birth was one of the first recorded of a manatee, making him the oldest one in captivity, and likely in the world.

The aquarium will remain closed during the investigation and while the staff grieves. A necropsy will be performed at the Florida Fish and Wildlife Conservation Commission's Marine Mammal Pathology lab in St. Petersburg.

Rest in peace, Snooty.