Two pedestrians strolling on a Soho street suffered “life-threatening injuries’’ Friday when they were struck by a metal fire-escape step that fell seven stories, authorities said.

The victims — a 27-year-old woman and 56-year-old man — were on the sidewalk in front of 38 Howard St. near Broadway when they were suddenly hit in the head by the plummeting piece of metal around 1:35 p.m., according to officials.

“I was about 10 feet away, sitting in my van, and I just saw a guy hit the ground. Blood starting pouring from his head,” said witness Matthew Kohere, 21.

“At first I didn’t know what it was. Honestly, I thought someone had shot him in the head, that’s how bad it was. I mean, there’s a lot of blood. He was out.”

Emergency responders rushed the pair to Bellevue Hospital with “serious, life-threatening injuries,” said FDNY Deputy Manhattan Borough Commander Michael Gala Jr.

An engineer hired by the building’s owner had been conducting a routine inspection of the fire escape when the step gave way, officials said.

“It was a normal inspection,” Gala said. “We had a woman up on the fire escape looking at the façade, and it appears that under her weight that step became dislodged.”

Gala said the inspector “actually fell partially through the fire escape, [and] thankfully she was able to pull herself up.”

The engineer refused medical aid at the scene.

Sakinah Bashir, 23, who works nearby at the Opening Ceremony clothing store, said he was startled by people “yelling and screaming.

“When I looked outside, there were [two people] on the ground — one was face up,” Bashir said. “One guy was clearly not moving. … We were all just trying to figure out what was going on.”

Passers-by on the street were stunned, too.

“I can’t believe it — that you could be just walking down the street and something falls from the sky,’’ said Hilary Stahlecker, 53. “It just goes to show you, it could happen to any of us.’’

The city issued a violation to the property owner after the incident for “failure to safeguard the building,” according to a Buildings Department rep.

The city last conducted a facade inspection report in 2013 and found no violations, said officials.

Additional reporting by Natalie Musumeci