A 24-year-old man was arrested for a fatal stabbing in Park Slope on Monday. Police sources say the suspect believed the victim had raped his girlfriend.

EMS found Manos Ikonomidis, 20, bleeding to death at 355 16th Street just after 4 a.m. on June 19th. Ikonomidis, who had been stabbed in the chest and had trauma to his body, was taken to Methodist Hospital, where he was pronounced dead.

According to multiple reports, Ikonomidis and another man had been engaged in a threesome with an unnamed woman. Police sources told DNAinfo that the woman "became upset after one of the men began to record the encounter and asked to be taken home."

The woman was reportedly driven home to Staten Island by the other man in the threesome and later told her boyfriend that she had been raped. The Daily News reports, "Ikonomidis’ girlfriend — who also was not involved in the sex play — received an ominous Instagram message reading 'your boyfriend f----d up and will be taken care of,' sources said."

Sources say that the boyfriend, Christopher Membreno, 24, and two other men went to the 16th Street building and confronted Ikonomidis, who lived in Gravesend, in a hallway, both stabbing him and beating him with a baseball hat.

Ikonomidis apparently crawled to Joy Liguori's apartment, knocking for help. "I saw the blood. It was out on the couch. That’s when I told him, ‘God, honey, you’re bleeding.’ He goes, ‘They stabbed me! They stabbed me twice! They stabbed me!’" she told the News. She added that he told her not to call 911, but she did anyway.

Membreno was arrested just after midnight today. He is charged with murder and criminal possession of a weapon.

The NYPD says the investigation is ongoing.