The Trinitarios gangbanger charged in the hit-and-run that injured a 4-year-old boy in Queens admitted to slamming into the kid with his gas-powered scooter — and then fleeing when an “aggressive crowd” surrounded him, prosecutors said Thursday.

Argenis Rivas, 29, also said little Jonathan Beauchamps “ran out” in front of him, according to a criminal complaint.

“I was just riding through the parking lot,” Rivas allegedly told cops, the complaint said. “I wasn’t doing wheelies. I wasn’t racing anybody. I hit the kid with the front of the scooter. He ran out from behind a car.

“I don’t have a license. My friends got kind of scared because there was an aggressive crowd and they told him, ‘Let’s go.’ I left in a car with my friends, in a gray Honda Accord.”

Rivas, who sources said is a member of the Trinitarios street gang, was ordered held on $15,000 bail Thursday in Queens Criminal Court.

Prosecutors alleged Rivas hit Jonathan while driving a “motorized gas scooter” around 5:45 p.m. Sunday as the tot played with his family in a parking lot of Meadowlake Trail in Flushing Meadows Park.

“What began as a recreational Sunday in the park turned into a nightmare for a Queens family,” Queens DA Melinda Katz, who sat in the rear of the courtroom during Thursday’s arraignment, said in a statement.

“As alleged, this defendant was illegally riding a scooter through the park when he recklessly hit a child and kept going. The city has seen an unacceptable increase in defiant drivers of all types of vehicles driving illegally and hurting people.”

“It is time we stand together and prevent further harm,” the borough’s top prosecutor added.

Sources previously told The Post that Rivas blamed the boy’s parents for the crash in a TikTok video.

He now faces charges including assault, leaving the scene of an accident, reckless driving, driving without a license and endangering the welfare of a child.

Rivas is accused of going as fast as 20 to 25 mph when he struck the boy — who was left bleeding from the head after hitting the ground, according to the complaint. The child was still unconscious when he arrived at the hospital, where he was intubated for three days, prosecutors said.

The boy’s family told The Post he was flung into the air and suffered a broken ankle and bruises to his liver and lung. He remains hospitalized at Cohen Children’s Medical Center.

Rivas was arrested Wednesday.

His family declined to comment as they left the courtroom Thursday.

Defense lawyer Maria Koutsogiannopoulos argued that her client should be released without bail, saying he has a full-time job and supports his family, including two children.

“Accidents happen, mistakes happen, things happen and I do believe Mr. Rivas deserves the opportunity to fight this case from the outside,” Koutsogiannopoulos said.

Judge Joanne Watters, however, ruled that bail of $15,000 cash or a $75,000 bond was appropriate to ensure Rivas returns to court given “the nature of the offense and what appears to be the strength of the case.”