A 28-year-old man shot a teenager to death then fatally shot himself in the head in a murder-suicide on a Queens street investigators suspect was sparked by a romantic rivalry, police sources said Sunday. The older man shot the 17-year-old victim in the chest near Oceania St. and 48th Ave. in Baysid e before turning the gun on himself about 10 p.m. Saturday, cops said. Medics rushed both men to New York-Presbyterian Hospital Queens but they couldn’t be saved. Investigators believe both men were dating the same woman, police sources said. Cops have not released the name of either man, pending family notification.   ...read more read less