Razor fiend: Granny scared me

A DERANGED man who randomly sliced the face of a 71-year-old granny on the subway in Manhattan tried to tell cops she may have been armed.

“I observed a silver object in her coat pocket and it made me lose it. I felt threatened,” said accused slasher Damon Knowles, 21, of Brooklyn.

Knowles was on a five-day crack bender when he encountered Carmen Rivera on Jan. 25 at 7 p.m. as the D train they were riding pulled into the Broadway-Lafayette station.

“I approached her and slashed her in the face with a razor,” he allegedly said. He also described the imaginary object as “an illusion”that caused him to “black out.”