A motorist who grew angry at a stopped Westbury intersection as Long Island Marathon participants raced by Sunday, soon walked naked onto the course and yelled incoherently before jogging briefly with other runners, Nassau police said.

Officers soon caught up with the unidentified man and took him into custody, Nassau police Det. Lt. Richard LeBrun said. The man was then taken by ambulance to a hospital for a medical evaluation, LeBrun said.

“He appeared to be aggravated because he couldn’t proceed through as traffic was being held up,” LeBrun said.

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Though some witnesses said the man was tackled by police, LeBrun said they tried to treat him as gently as possible because they didn’t see him as a terrorist but someone in need of medical help.

The man was not arrested, LeBrun said. But when he took off among the runners, officers quickly moved in and threw a sheet over him.

“We placed him in soft restraints — not handcuffs — they were very flexible as to not injure anybody,” LeBrun said.

Marathoners who ran by the man as he stood near the side of the course with no clothes, said, to say the least, it was an unnerving moment for an otherwise festive annual Long Island staple.

“He was really close,” said John Tupper, 26, who competed in Sunday’s marathon events and ran by the man. “You could see everything. He was just shouting and rambling . . . a lot of foul language.”

By the time Frank Chu, 40, of Jericho, said he was hitting mile marker four, the man was running in the opposite direction of the racers, mumbling about ruling the world.

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“A lot of crazy stuff,” Chu said of the man’s ramblings. “Totally naked.”

LeBrun, who declined to identify the man, said he was driving a four-door sedan and was alone in the car when he decided to jump out and take his clothes off.

The incident occurred shortly after 8:30 a.m., police said. The man was upset he couldn’t get through the Merrick Avenue and Privado Road intersection because it was blocked for the marathon, LeBrun said.

“He parked his car and walked into the middle of the pack of runners, screaming anti-government rhetoric,” LeBrun said. “He kind of jumped in there and also started running a little bit.”

With Candice Ruud