Times Square was packed with thousands of tourists and office workers — lured outdoors on a hot, sunny day — when a car suddenly came at them.

Pandemonium erupted during lunch hour Thursday as the maroon Honda Accord rumbled down crowded Manhattan sidewalks.

The lucky ones in the vehicle’s path managed to dive out of the way. Others were simply mowed down.

Screams filled the air, soon to be followed by sirens.

“All hell broke loose,” said Moro Omar, 32, who was standing at the corner of 42nd Street and Seventh Avenue.

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Witnesses said they saw pedestrians get hit by the Honda as it barreled past tourist draws like the Hard Rock Cafe and Bubba Gump Shrimp Co.

Charlie Smith, 26, of Manhattan, was holding a sign hawking $10 lunch specials at 41st and Seventh when he heard a loud crash.

Then he saw dozens of panicked people running down the avenue as fast as they could — “screaming, really scared.”

Police said the Honda drove north on Seventh Avenue sidewalks — a one-way, southbound thoroughfare — for several blocks before slamming into a security barrier. The driver, Richard Rojas, 26, of the Bronx, was arrested.

What had begun as a pleasant day had turned in an instant into a nightmare.

An 18-year-old woman from Michigan was killed and 22 others injured, police said.

Streets were left littered with victims. People rushed to offer as much help as they could, but Omar said the woman who died was beyond help.

“Unfortunately, there was nothing we could do so we waited for the ambulance to come,” said Omar, a ticket agent for TopView Sightseeing who lives in the Bronx.

Duane Jackson, who was selling T-shirts on 45th Street, said he saw one man get knocked back about 10 feet after being struck by the car.

“I went over to the guy and he was laying on the ground,” Jackson said. “His family was around him.”

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Many in the crowd heard the screams and feared the worst: a terror attack.

“Here we go again,” Jackson remembered thinking. Terrorists have used vehicles in recent months to attack pedestrians in Britain, France, Germany, Israel and Sweden.

Visiting from Wisconsin, Kelly Graves, 54, was in Times Square with her husband. They were waiting to get on a tour bus when they heard the crash.

As “chaos” erupted around them, Graves said she thought maybe a bomb had gone off.

“We could see them all laid across the ground,” she said of the injured. “We saw flames coming off of the car. It was scary.”

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James Knudsen, 52, of Long Island City, was about to leave work for lunch when the mayhem started.

Knudsen, an event lighting director at the nearby Marriott Marquis, could have become a victim. But afterward he showed a New Yorker’s grit.

“I’ve worked in Times Square for over 20 years,” he said, “so I’m not too rattled by it.”