NORTH PHILADEPHIA (WPVI) -- A man armed with a butcher knife was shot and killed by a security guard inside a North Philadelphia cell phone store Tuesday afternoon.The shooting happened around 12:31 p.m. at My Phillie Wireless in the 2700 block of North Broad Street.Police say the knife-wielding man ran behind the counter but was shot by the guard.The suspect was hit in the chest and was pronounced dead at the hospital.That man's name has not been released.