To expand on the headline, the 19 year old was dating the 15 year old, and was involved in a sexual relationship with her.
The father of the girl, in wanting to put a stop to the relationship, reported the kid to the cops, who then arrested him and charged him with a slew of crimes related to the endangerment of a child.

Here’s the deal: Do you feel this kid’s life should be ruined because he was having sex with someone who turns out to be his 15 year old girlfriend?

According to this:

Andrew Laureano is charged with second-degree sexual assault and third-degree endangering the welfare of a child. He was arrested last Wednesday.

Lt. Thomas Kmetz said the girl's father notified police his daughter had been in a sexual relationship with Laureano.

Hopatcong Detective William Sutphen and a detective from the Sussex County Prosecutor's Office investigated, and interviewed Laureano and the girl, he said.
Kmetz wrote in a press release on the incident…."It was found that the two had a sexual dating relationship for several months."

Laureano was lodged in the Sussex County Correctional Facility in lieu of $50,000 bail.

After Hopatcong police posted a notice about the arrest on Facebook — as they typically do for arrests — several area criticized police for making the arrest, and for publicizing it. Some also criticized the girl's father for reporting the relationship.

Sean McManus wrote "So, (you) have 21-year-olds marrying 30-year-olds. Guess people forget there's a lot of people that turn 18 senior year, so if (you're) dating someone at that point (you) just gotta break up with them (whether you) like it or not,". "I agree though, no reason to be putting people's business all over Facebook let alone something like this."

But Kmetz replied that Hopatcong police issue press releases for all arrests.
"And we don't make the law, we enforce the law," he wrote. "If you want it that adults can have sex with minors, call your elected officials to change the law. Don't put down Hopatcong as making something out of nothing. This is a second- and third-degree crime, not a borough ordinance for littering."

One commenter sums up the situation perfectly:

I don't know if this guy deserves to live with the title of sex offender for the rest of his life + a possible long prison sentence in state penn.

Understanding full well that the age of consent in the state is 16, and that, technically, his allegedly having had sex with his girlfriend is a crime; do you really and truly believe in your heart he would be a candidate for lifetime supervision under Megan’s Law.

Which is what would happen if found guilty.

Guilty of having had sex with his girlfriend!