An NYPD sergeant fatally shot himself in a car parked outside the 66th Precinct Station House in Brooklyn Thursday night. Law enforcement sources say the officer, who was about to become a detective, had just made a robbery arrest. He told colleagues he needed to get something from downstairs and never came back. A source told the Daily News they had no idea he was suicidal. "People always say, 'The signs, the signs,' but there were no signs," said the source.