The 17-year-old boy who was stabbed to death on a Brooklyn street this week had instigated a fight with a fellow teen before he was knifed, police said Wednesday.

Police questioned a person of interest in the death of Alex Colodner, who was stabbed numerous times in the torso, just before 4 p.m. Tuesday in Bedford-Stuyvesant.

But by Wednesday morning, Chief of Detectives James Essig said the act had been ruled self-defense by prosecutors — and the suspected stabber was released without charges.

Investigators found Colodner had shown up to the other teen’s home to confront him after Colodner’s girlfriend said the boy had been flirting with her, according to Deputy Chief Kevin Maloney.

Colodner, who weighed 100 pounds more than the other boy, began to beat him.

As Colodner was “getting the best of him,” the teen pulled a knife and stabbed him eight times, Essig said.

Colodner was rushed to Kings County Hospital Center, but could not be saved and died hours later.

Prosecutors could still choose to present the case to a grand jury to charge the stabber, Essig said.

The Brooklyn District Attorney’s Office did not comment.

Colodner’s father was too overcome with grief to speak, telling The Post from his Brooklyn home, “I need to mourn” before shutting the door. 

The deadly bloodshed — which took place on Quincy Street near Marcus Garvey Boulevard — left Colodner’s neighbors reeling.

“He was a kid — a big, soft giant,” said one local resident of Colodner, who went by the nickname “Sumo.”

“He was tall but never hurt anybody,” the neighbor added.

Another neighbor said, “Even if it was over a girl it shouldn’t have to come to this.”

“It’s terrible out there in the streets — the guns, the violence. Something needs to change.”

Additional reporting by Craig McCarthy