Metro

Nuts beau ‘stab slay’

A violence-prone Brooklyn man stabbed his girlfriend to death and then turned his knife on himself in a botched suicide yesterday, police sources said.

Alexander Santiago, 44, nearly decapitated girlfriend Tara Beardsall, 31, in their Sunset Park apartment at 10:30 a.m. yesterday, said the sources. He then plunged the knife into his own neck but couldn’t finish the job, the sources said.

Neighbors of the couple’s apartment on 51st Street said they saw Beardsall stagger out of the building and collapse, her clothing soaked in blood.

The couple had a history of domestic violence — including an incident Dec. 22 in which Santiago attacked Beardsall with a knife and held her hostage, said the sources.

Beardsall told authorities after that incident that if he was released, he would kill her, the sources added.