Ex-girlfriend questioned over man’s stabbing death

A man was stabbed to death in Brooklyn Tuesday afternoon, cops said.

The 18-year-old was stabbed at least once in the chest inside his Prospect Lefferts Garden apartment on Parkside Avenue near Parkside Court around 2:45 p.m., cops said.

Police are questioning the mother of his young son who was in the apartment at the time, and with whom he recently split, sources and neighbors said.

Tuesday night police identified the deceased as Alexis Martinez, 18.

“I’ve seen them together and they seem very happy,” said Abigael Taltelpa, 24, who lives upstairs. “This is sad for his baby.”

The father who worked in construction and went to school was dedicated to his toddler, a friend of the victim said.

“He would go to school and work all day,” said Kimberly Salas, 19. “He would always focus on his kid. It’s tragic that this would happen.”

One neighbor said in recent months he frequently heard the parents arguing.

“I don’t want to believe his girlfriend did this,” said Salas. “I didn’t know her well but she seemed calm and friendly like him.”

EMS transported the victim to Kings County Hospital in critical condition where he died, officials said.