A deranged knife-wielding attacker fatally stabbed a 69-year-old man in the back inside a Chinatown apartment, police said Sunday. Feizhon Zheng, 50, was busted for murder for the stabbing, which unfolded at 7 Eldridge St. around 3:50 p.m. on Saturday. It’s unclear how Zheng knew the victim, whose identity hasn’t been released pending family notification….
