5 people stabbed at NYC's Penn Station. Here's what we know.

Law enforcement responded to reports of five people stabbed at Penn Station on Sunday evening.

At least one injury was said to be serious in the attack, which happened at around 7 p.m. Amtrak Police launched a manhunt and a suspect was quickly taken into custody, Amtrak said in a statement.

Police sources say a knife was recovered from the scene.

The victims were taken to Bellevue Hospital. The conditions of the other four were not immediately known.

Police asked the public to avoid the area as there were expected to be traffic delays, road closures, and mass transit disruptions.    

What we know about the suspect

Video shows at least four Amtrak officers apprehending the suspect at the scene. One witness said the officers pepper sprayed the suspect and then tackled him.

"They had to get other cops in order to grab him," the witness said.

The suspect is described as an emotionally disturbed person with no terror links, police sources said.

"He was just screaming, waving his head around," witness Michael Christian said. "I've seen him once, but I didn't think he was capable of doing anything."

Random act of violence, source says

A law enforcement source close to the investigation told CBS News that preliminary reports suggest it was a random act of violence.

A high-ranking NYPD source said the stabbing had "no terror nexus."

"I am deeply disturbed by reports of a stabbing at Penn Station that left multiple people injured," City Council Speaker Julie Menin wrote on social media. "My thoughts are with the victims and their loved ones, and I am grateful to the first responders and law enforcement officers who quickly secured the scene and took the suspect into custody. We are in touch with the NYPD and will continue to monitor the situation closely as we await additional information."