The man accused of the murder that sparked a summertime mass shooting in Brooklyn gave a “full confession” — and was only brought down thanks to community tipsters, police said Thursday.

Kyle Williams, 20, was arrested Wednesday and later admitted to shooting dead 38-year-old Jason Pagan July 27 at the Old Timer’s Day block party in Mendoza Park in Brownsville, Deputy Chief Michael Kemper said.

A second suspected shooter was taken into custody Thursday, though he hasn’t yet been charged, police said.

The NYPD finally got their big break in the months-old case two weeks ago when they released a video of two women wanted for questioning.

That’s when “tips started coming in,” said Kemper, adding: “The identity of those two females, along with other evidence that we already had, led us to the murderer.”

Williams shot Pagan — a rival Bloods gang member — in the head after the pair got into an argument about an old beef at the community fair, police said.

Investigators believe a friend of Pagan — who was in custody Thursday — returned fire, sparking a shootout that injured 11 other people at the party.

A semi-automatic weapon used to fire into the crowd was recovered in a building in Brownsville after a tip from a neighbor — leading police to Pagan’s pal, they said.

He is likely to be charged with felony assault and attempted murder, police said.

“This case is still very active,” Kemper said, thanking the Brownsville community for their help.

“It’s very rewarding for [detectives] to be in the position right now to let Jason Pagan’s family… know that the murderer of her son was apprehended and arrested and confessed. It’s justice.”