Police are looking for a man they said fatally shot a Bronx man — who officials said was dating the suspect's ex-girlfriend — on the ground floor of his apartment building Saturday morning.

Officers said they found Juan Flores, 49, around 7:25 a.m., shot in the back, in his apartment building on Webb Ave. near West 197th St. after a neighbor heard a gunshot and saw a person flee the scene.

The victim was pronounced dead at a local hospital.

The city police department said the man seen in the lobby of a surveillance video, seen in the video above, is believed to be the gunman and appeared to have used a sawed off shotgun.

Police identified the man seen leaving the scene as 49-year-old Jose Quinones, seen above.

Officials said he was last seen wearing a red shirt with "21" and "Puerto Rico" written on it, dark shorts, and dark sneakers.

Anyone with information on the case should contact the Crime Stoppers hotline at 1-800-577-8477, or text CRIMES and then enter TIP577, or visit www.nypdcrimestoppers.com