NEW YORK — Federal agents raided the offices Tuesday of a New York City police union, the Sergeants Benevolent Association, and the Long Island home of its bombastic leader, who has clashed with city officials over his incendiary tweets and hard-line tactics.

FBI spokesperson Martin Feely said agents were "carrying out a law enforcement action in connection with an ongoing investigation."

Agents were seen carrying boxes out of the union's Manhattan headquarters and loading them into a van. The FBI also searched union president Ed Mullins' home in Port Washington, Long Island, Feely said.

Mullins resigned as the union's president Tuesday night at the behest of its board, according to a message the union sent to its members. The union represents about 13,000 active and retired NYPD sergeants and controls a $264 million retirement fund.