A crazed straphanger stabbed an elderly man in the face with a pair of scissors on a downtown Brooklyn train early Saturday, cops said.

Evan Hemans, 27, hopped on a Manhattan-bound Q train at the DeKalb Avenue station just before 1 a.m., clutching the scissors, according to police.

Most people in the car bolted when they spotted Hemans, but a 72-year-old man with a cane stayed put, cops said.

Hemans then stabbed him in the face with the scissors before running from the train, according to police.

It wasn’t long before cops, who heard a description of Hemans over the radio, arrested him outside the station.

Hemans, of the Bronx, was charged with assault, criminal possession of a weapon and harassment, according to police.

The elderly victim was taken to Methodist Hospital in stable condition.