A homeless man stabbed a porn watcher at Brooklyn Heights public library for watching lewd videos on a publicly accessible computer Tuesday, police said.

The homeless man, Ralph Neptune, stabbed the alleged porn watcher, an unnamed 52-year-old man at the Brooklyn Heights branch of the Brooklyn Public Library. At around 7:20 p.m., he and his wife spied the man abusing his computer privileges on the second floor- that's where things got ugly.

"He was with his wife and he accused the other guy of looking at porn," a police source told the New York Daily News.

The 52-year-old victim didn't take kindly to being accused publicly, and confronted Neptune, which began an altercation.

"The guy looking at porn picked up a chair and hits him," continued the anonymous police source. From there, things only escalated, and ended with the man being knifed in the library.

"The guy who was offended said, 'I have a knife,' and stabs him in the chest," said the insider.

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When the homeless man viciously attacked the man watching adult videos, his wife screamed aloud, witnesses told the Daily News. Apparently, the couple was from Peekskill.

"How are we going to get back to Peekskill?!" she screamed, according to the source.

Police, fire, and emergency services were alerted to the incident, and arrived at Brooklyn Public Library, where they found the victim still conscious. The middle-aged man was wheeled out of the library in a wheelchair still talking.

The man was then taken to Bellevue Hospital for treatment. Although blood could be seen, the wounds he received were not life-threatening.

As for Ralph Neptune, he was arrested. His charges for the stabbing were assault, criminal possession of a weapon, and menacing. Police also charged him with criminal possession of marijuana, which could explain his irrational behavior.