A former NYU instructor went on a bizarre rampage in Brooklyn — yelling at a pooch and splashing a woman with a liquid he claimed was blood, sources said yesterday.

Hans Shmidheiser, 30, approached a man walking his dog in Williamsburg around 8 a.m. on Friday, picked the pup up and asked it, “What the f–k is your name?” sources said.

The terrified owner fled and called cops.

An hour later, Shmidheiser — who taught at NYU from 2004 to 2008 while getting a Ph.D. in math — walked up to a female pedestrian. “He said he wanted to go to the hospital because he was drinking a lot of blood,” she told The Post.

Shmidheiser then doused the poor woman with red liquid and told her it was blood, according to sources.

It turns out the liquid was just fruit punch, she said.

Cops arrested him shortly afterward. He faces misdemeanor charges of menacing and harassment.