An off-duty NYPD officer was injured in an early-morning shooting in University Heights, and police say three suspects are in custody.The shooting occurred on Pelham Place at around 5 a.m. as the officer, 12-year veteran Nelsen Vergara, returned home from work.Police Commissioner Ray Kelly says Vergara was walking home when a group of men drinking beer on a porch threw a bottle at him. As he approached the men and identified himself as a police officer, a green Honda pulled up and the driver stepped out and opened fire, according to Kelly. Vergara, a Marine who served two tours in Iraq, was hit in the back and arm, but still managed to apprehend the suspect who threw the bottle at him, Kelly says. Vergara also returned fire at the man who drove up. The suspect in the green Honda fled and drove himself to Bronx-Lebanon Hospital, police say.Police officials say a total of three suspects allegedly involved in the incident are in custody, although their names have not yet been released. Five more people are also being questioned in connection with the incident.Vergara, a father of two, is in stable condition and is expected to recover. Mayor Michael Bloomberg called him a hero as he spoke from the hospital about the case this morning.