A Brooklyn man who had previously been shot was warned not to testify before a grand jury about the incident by thugs wearing masks and wielding baseball bats, police sources said Sunday.

Alejandro Negron, 34, told cops he was leaving his Williamsburg home around 12:45 p.m. Saturday when he was threatened by two men over the investigation into his Dec. 6 shooting during a robbery.

“Don’t go to court. Don’t testify. You know what you did,” the men said, according to police sources.

Negron fled back into his home.

Nearly a month earlier, Negron had been shot four times during a robbery that occurred around 9:30 p.m. as he left the Airway Inn near La Guardia Airport, police sources said.

He told cops that the thugs made off with his $20,000 necklace.

Jose Hernandez was arrested Dec. 10 after Negron picked him out of a photo array and a line-up, sources said.

Hernandez was charged with attempted murder, assault and robbery in the first degree. He is set to next appear in court Friday, records show.