A Suffolk County cop fatally shot a knife-wielding madman who allegedly charged out of the woods to finish off his bloodied victim, officials said.

A 14-year-old boy and a 17-year-old boy were both stabbed at the Huntington Manor Fireman’s Fair on Tuesday, according to the Suffolk County Police Department.

One boy, 14, was stabbed and seriously injured. A second boy, 17, sustained stab wounds not considered life-threatening, according to investigators. Both teens were taken to hospitals for treatment.