The maniac who allegedly slapped two kids, one only a toddler, in a disturbing outburst on the High Line was arrested Thursday.

Rammy Lopez, 32, of Brooklyn, allegedly whacked a 7-year-old boy as he walked with his 3-year-old sister and babysitter on a day off from school, around 12:30 p.m. Wednesday, according to his mom, who declined to give her name.

"They were walking on the High Line to go to the Whitney," his mom told The Post by phone. "And from what he told me, the guy walked by him and hit him in the mouth, jaw area with his phone."

"He said, 'Don't you dare do that again' or something equally nonsensical," the boy's mom added. "[He] just hit him and left."

The babysitter made sure the shaken boy was "safe and calm" - and then called his mom, who rushed to the scene from work in Brooklyn.

"He said he was fine, but he was crying pretty hysterically," she said. "It's scary, you know."

"He said his jaw hurt, and that one of his teeth [was] loose, but he was more startled than injured," his mom added.

A short time after the attack on the 7-year-old, the deranged stranger allegedly slapped a 2-year-old girl in the face as she sat with her father nearby, cops and sources said.

The attack left the tot - who is from Israel and joined her dad on a trip to the Big Apple - with bruising, redness and swelling, sources said.

Lopez - who sources described as an "emotionally disturbed person" - took off and stayed on the lam until cops caught up to him in Brownsville Thursday morning, police said.

He was charged with two counts of felony assault, according to cops.

The older victim's mom credited the responding cops, saying they did all they could to help.

"The police were excellent," she said. "They made all of us feel very confident they were going to find him. And they did."

Lopez was most recently arrested on forcible touching charges from late August, also in Manhattan, according to sources and online records.

He was released on his own recognizance during that arraignment, the records show.

"My guess is that we probably should do something better for getting people options when they get back on the street, or getting them the mental help that they need," the boy's mom said.

Meanwhile, she said it can be difficult to protect kids from harm on the streets of the city.

"I'm a small woman, right? My son is almost as big as me," she said. "How do you keep them safe? You know? You can't protect them against everything."

Maniac arrested for allegedly slapping 2 kids, including toddler, on...