Mary Cox was on duty and leaning on a Honda Accord on the northeast corner of 34th Avenue at 82nd Street about 10:46 a.m., when a Honda Odyssey minivan slammed into the car and knocked her to the ground, NYPD and FDNY officials said.
The Accord's owner, who said his name was Chris, was with his wife in a nearby a physical therapy office when the crash occurred.
"I heard a really loud bang, and came outside," he said.
There, he saw Cox lying next to his car, bleeding but conscious, he said.
Cox, who's been a guard for seven years and lived about a block away on 81st Street, hit her head and was taken to Elmhurst Hospital in critical condition, police said.
Her condition later improved to stable and tests showed she escaped suffering any internal injuries, said her eldest son Michael Turek, 55.
"[She had] a bump on the back of her head and a gash," Turek said outside the hospital.
Cox, a widow, is a mother to three daughters and four sons, one of whom died in 2014, friends and family said.
Turek said he was "very relieved" that her condition improved.
Cox was near her post because P.S. 212 School for CyberSecurity and Literacy was let out early at 11:30 a.m. for parent teacher conferences that afternoon, according to the school's website.
It was not clear if children were around at the time.
The elementary school enrolls about 788 students between kindergarten and fifth grade, according to the Department of Education.
The crash occurred within a city-imposed slow zone with a 20 mph speed limit that is meant to curb pedestrian injuries.
It was not immediately clear if speed was a factor in the Thursday morning incident.
The driver of the Honda Odyssey remained on scene throughout the day, but did not want to speak about the accident.
Neighbors who know the guard were saddened to learn that she was hurt.
"She is a very nice lady. She always helps me when I cross with my son," said Nadia Nodi, 25, who has known Cox for three years and lives in the same apartment building with her.
"She's very dedicated to her job and great with kids," the mother added.
The minivan's driver remained on the scene.
Police did not immediately suspect any criminality was involved in the crash.