An off-duty New Jersey state trooper saved a choking two-week-old infant after a neighbor ran to his door looking for help, police said.

Trooper Robert Meyer woke up to a knock at his door Saturday afternoon after returning from a night shift, police said. The neighbor went to Meyer’s house when he noticed a marked law enforcement vehicle parked outside.

The neighbor, who Meyer never met and but lives four houses down from, told the off-duty officer her two-week-old granddaughter Elizabeth was choking.

"While she was feeding, she vomited, and it was vomit and mucus that got caught in her nose and throat," Meyer said at a news conference on Monday. "And we saw a lot of babies getting suction, they're all small, there are a lot of complications."

Police said Meyer dashed out of the door without shoes on.

"I saw him flying out of the front door with no shoes on, just bed clothes on," Peter Jackey, a neighbor, told ABC7NY.

Police said the newborn was “blue and struggling to breathe” when the trooper arrived. Meyer told reporters he attempted to pat the baby’s back to free up her airway, but it didn’t work.

"I asked if anyone had any suction that I'd be able to use to clear her airways. Luckily, the dad did have one,” Meyer said.

The bulb syringe cleared up Elizabeth’s airways and she began breathing. She was taken to the hospital and released later Saturday.

The infant suffered no serious injuries and is expected to make a full recovery, police said.