An explosion at a Pennsylvania nursing home killed at least two people and left multiple elderly residents and staff members trapped inside — as firefighters rushed to battle the flames Tuesday afternoon. The large blast erupted around 2:15 p.m. at Silver Lake Nursing Home in Bristol Township, about 21 miles northeast of Philadelphia, igniting a fire that tore through the building and prompted officials to declare a mass casualty incident, according to the Upper Masefield Township Police Department, WFMZ reported.