A tragedy has befallen the U.S. special operations community as a Special Forces staff sergeant died in a drowning accident on Tuesday. The drowning occurred during a training event of the intense Combat Diver Qualification Course (CDQC).

“The Staff Sergeant was a student in the Special Forces Combat Diver Qualification Course, and was participating in a conditioning exercise in the pool, which stresses the students’ cardio, respiratory and muscular endurance,” according to a press release from the Army Combat Readiness Center and the John F. Kennedy Special Warfare Center and School (SWCS) cited by Military Times.

According to the press release, the staff sergeant belonged to the 10th Special Forces Group.

The death happened at the Army’s Special Forces Underwater Operations School, in Key West, Florida.