The 14-year-old boy who leaped to his death in front of his horrified family at the Vessel in Hudson Yards was laughing and running with his sister right before, according to a worker who witnessed the tragedy.

“There were lots of tourists around. The kid was racing up the stairs with his younger sister and having a blast, having so much fun,’’ said a security guard at the Manhattan tourist attraction to The Post on Friday, a day after fatal jump.

“One of my colleagues told them, ‘I know it’s fun and stuff, but you are not allowed to run in the Vessel,’ and, ‘Stay with your parents.’ Somehow, when he got to Level Eight, he jumped,” the guard said of the teen from upscale Livingston, New Jersey.

“I saw his parents after,’’ the worker said. “The lady panicked. She was screaming and crying. The father was speechless. The sister was crying.”

The security guard added, “I heard the impact. I saw [the boy] was wearing a colorful shirt. My heart just dropped.”

Police sources said the teen had a history of depression and had attempted suicide before.

A grieving family friend who was outside the parents’ home Friday told The Post, “The funeral is tomorrow.”

“He was a very sweet kid, very smart,’’ the friend said of the boy, whose grandmother also was with the family when he killed himself. “We’re dealing with it. These things are never easy.”

The boy’s death marked the fourth suicide in two years at the 16-story modern landmark along the Hudson River in Midtown — and it may now be shut for good because of all the tragedies.

The structure was closed after the teen’s death, and the site’s developer Stephen Ross, told the Daily Beast on Thursday he doesn’t know if it will ever reopen.

“They tried adding more security, but it didn’t help,’’ the guard said.

Another security worker noted, “There are ‘ambassadors’ on floors four to eight because [those sections] are bigger and higher.

“Ambassadors make sure people are following the rules, not doing what they are not supposed to do. But we respect [visitors’] space, we keep our distance, because they are tourists.

“They are here to enjoy themselves, but we do keep an eye on them. We make sure the kids are not running around.”

Chrishawn Jordan, 26, who works as a bike mechanic nearby, added, “It’s supposed to be a tourist attraction, but it has definitely become a death attraction.”

“They definitely need more security, for sure,’’ he said.

Ross did not respond to requests for comment Friday, nor did the site’s security management company.

A family of Alabama tourists was among the droves of people who went to the striking attraction Friday hoping to climb it, only to be told it is indefinitely shut.

“We are a little disappointed. We were looking forward to the view,” said a man who only gave his first name, Raj, while holding a camera in one hand and surrounded by his wife and three kids.

“It’s tragic,’’ he said of the teen’s death.

“They could have done a better job when it comes to safety. They could have made the balconies higher. They should consider enclosing the top floors with glass, because you are here to see the view only,” he said.

Anyone suffering from suicidal thoughts is urged to call the National Suicide Prevention Lifeline at 800-273-8255 text HOME to 741741 or visit SpeakingOfSuicide.com/resources for additional resources.

Per: NYP