A TikTok troll was arrested and charged Friday with fatally stabbing a 17-year-old boy, who inadvertently got between the online-provocateur and an angry mob that came to his home to confront him over claims he raped a young child, sources said.

Andrew Tollinche, 22, allegedly stabbed high school student Jonathan Melo in the back Wednesday after the teen victim got caught up in the showdown at a Bronx apartment, which was sparked when Tollinche dared people on TikTok to face him down over the sex allegations, law enforcement sources said.

During the encounter, Tollinche allegedly grabbed a large kitchen knife from his home and went outside to send the angry people fleeing, but allegedly wound up stabbing Melo amid the chaotic scene, sources said.

It was not clear why the high school senior was at the location on Beach Avenue in Soundview — as he lives a few miles — but sources said he was not part of the mob that confronted Tollinche. He was rushed to Jacobi Hospital and pronounced dead.

Tollinche is facing second-degree murder, manslaughter and criminal possession of a weapon charges and pleaded not guilty during his arraignment Friday.

The new charges come after he had already been charged in September with allegedly raping the pre-teen, in a case that remains active, police said.

He had pleaded not guilty to counts of rape, promoting sexual performance by a child, possessing sexual performance by a child and endangering the welfare of a child.

A judge released him in that case, but required he wear an ankle monitor, sources said.

His lawyer, Edgar DeLeon, told The Post that his client has been subjected to violence and threats since the rape case came to light.

Deleon called Melo’s death a “tragedy” regardless of the circumstances surrounding the fatal incident, but largely declined comment on the murder charge his client is facing.

Melo’s mother previously told The Post on Thursday Jonathan was “at the wrong place at the wrong time.”

“Jonathan was so full of life. He was the clown of the house, he was so vivacious. He always wanted to be active and loved basketball,” Raquel Melo said.

“He loved working out. That was something new that his father and him were bonding over, and he loved his family.”