Officials said the driver, who was not injured, apparently mistook the accelerator for the brake at the Amberwood Gardens Skilled Nursing and Rehabilitation Center at about 9:45 a.m.
The car went into a common room where residents suffering from dementia were gathering for exercises.
"I turned around and saw this car in the room 10 feet from me," said Eric Chin, an activity leader for the center who was in the room. "You could hear glass breaking. A whole chunk of wall was gone. It was scary."
Chin said the driver was in tears and appeared to be shocked.
The person who died was reportedly an 88-year-old woman. One staff member was among those injured.
The Associated Press contributed to this report.