A 36-year-old police officer and three other people were shot and killed, and one other injured, by a crazed gunman who stormed a swanky Midtown skyscraper early Monday evening — before turning the gun on himself, police said. The 27-year-old maniac, identified by sources as Shane Tamura, barged into the 44-story building — which houses Blackstone and the NFL headquarters — armed with a rifle and opened fire at around 6:30 p.m. during the evening rush, cops and law enforcement sources told The Post.snipMeanwhile, two apparent protesters, including one who yelled, “Free Palestine, I’m not the shooter,” were arrested outside...