A man believed to be in his early 30s was shot and killed Friday in Mattapan, Boston police said. Police responded at about 3:12 p.m. to reports of a shooting on Gladeside Avenue, where they found the victim suffering from multiple gunshot wounds. The man, who was not identified, was taken to Boston Medical Center, where he was taken into surgery before being pronounced dead. Police said they are pursuing “several substantive leads.” No other information was immediately available Friday night.Juan Cajigas can be reached at Juan.firstname.lastname@example.org. Follow him on Twitter at @Esteban_Cajigas.