At least seven guns were fired during the gang-related shootout that killed an aide to Gov. Cuomo — including one weapon that was used in another unsolved homicide, The Post has learned.

Cops found 24 shell casings littering the area where Carey Gabay got caught in the crossfire during a violence-prone street celebration preceding the annual West Indian American Day Parade in Brooklyn, law-enforcement sources said.

Ballistics testing tied some of the shells to a handgun used to shoot three young men — one fatally — in the Brownsville section of Brooklyn on the evening of Aug. 13, the sources said.

Surveillance video of that incident released by the NYPD shows a masked gunman pushing open the front door to an apartment building and spraying the lobby with bullets.

One of the victims, Isaiah Cicero, 21, was pronounced dead from a wound to the torso.

Cicero was a reputed member of the Bully Gang, and his killer is believed to be a member of the rival Hood Starz, the sources said.

Cops also linked shell casings found near Gabay’s Sept. 7 shooting to a gun that was used to wound a man in East New York and a firearm that was used to damage a car elsewhere in Brooklyn, the sources said.

The 9mm slug that killed Gabay — and was retrieved from his head after his death — came from a pistol that hasn’t yet been linked to any other crimes, the sources said.

Several gang members, including some from the Hood Starz, are believed to have taken part in the shootout that killed Gabay, a Harvard-educated lawyer who worked in Cuomo’s administration.

Detectives have the names and nicknames of various people who were present at the scene, but don’t yet have any suspects in Gabay’s slaying, the sources said.

Gabay, 43, was shot once in the top of the head as he ducked for cover from gunfire that erupted while he was walking home from the annual street celebration known as J’Ouvert.