Updated: 13 AUG 19 09:17 ET

By Shimon Prokupecz and Brynn Gingras, CNN

(CNN) -- Another New York Police Department officer has died by suicide -- becoming the eighth to do so this year -- a law enforcement official told CNN.

The 35-year-old was a seven-year veteran who temporarily was assigned to a detail surrounding Yankee Stadium.

The officer left a note behind, the law enforcement official said. He was off-duty at the time, two law enforcement sources told CNN.

Of the eight NYPD officer suicides, six have happened since June. The recent cluster has rattled the department, with leaders trying to come up with a way to tell the rank and file that it's OK to ask for help.

Over the past five years, the NYPD has averaged between four and five suicides a year, Police Commissioner James O'Neill said in June at a news conference that was called after the department surpassed its average.

Developing story. More to come.