A 32-year-old staffer at an out-patient medical facility affiliated with Columbia University was stabbed by a patient Wednesday morning, police said.

The suspect, a 25-year-old man from Brooklyn, had an appointment at ColumbiaDoctors Midtown, a facility on the third floor of a West 51st Street building, police said. But it all went wrong when he pulled a knife at about 10:30 a.m.

The victim, who was not identified, was taken to Cornell Medical Center with non life-threatening injuries.

Elyce Ponte, 55, a nurse from Allentown, Pennsylvania, was in the waiting room when the chaos erupted. She said the suspect appeared to be "on a mission." Ponte said she dove behind a couch as another woman, who was leaving the stairwell, saw the suspect and started to scream.

"That's what alerted everyone really, because there wasn't any code red or anything," Ponte said. "I was never really scared, I knew security was going to be right on him. If he had a gun it would be a totally different story."

Ponte said the man was holding the knife, a few inches long, by his waist.

By the time police got there, the suspect no longer had the knife, and investigators were able to recover it.

It was not immediately clear why he pulled a knife on the man, who appeared to be a stranger.

The suspect was taken to Bellevue Medical Center for a psychiatric evaluation, police said.

By Monday afternoon everything appeared to be business as usual. A crowd that gathered earlier in the morning had disbursed and the only sign of the violence was a few officers standing guard.

"A staff member at our ColumbiaDoctors West 51st Street clinical practice suffered a non-life-threatening knife injury," said a spokeswoman for Columbia University Medical Center. "We are grateful to all the first-responders to this unfortunate event, including the FDNY and NYPD, and wish our staff member a quick recovery.  Any further questions should be directed to NYPD."