Police say the roof of the Grand Theater in Williamstown collapsed around 3:15 p.m.
Two residents of an apartment at the front of the building were hurt. Neither injury was considered life-threatening.
Daniel Bates, 47, was hurt when he fell down the stairs while trying to evacuate his wife and their two young grandchildren, police said. He was being treated at Cooper Hospital.
His wife Gail, 48, was taken to JFK Hospital in Turnersville.
The grandchildren, ages 2 and 1, and the family dog and cat got out safely.
"My whole life was in that building," Gail told Action News Friday evening.
The area the roof that caved in was over the rear portion of the building, which houses a 450-seat playhouse.
Built in 1924, the theater is currently home to the Road Company, a theater troupe.
Police say the roof might have been damaged by the winter's heavy snowfall.
Problems with the roof forced the company's recent production of "The Sound of Music" to be moved to a nearby school auditorium.
