- Suspect appears to have mental problems, police say
- Police believe the suspect acted alone
Police described the suspect, who lives in nearby Wuppertal, as "a 36-year-old man from the former Yugoslavia."
He "obviously has mental problems," Dusseldorf police said in a statement.
Of the seven people wounded in the Thursday night attack, three suffered severe injuries. Two women were among the injured.
Police believe the suspect acted alone.
Bruno Macedo, a passenger on a train that was due to stop in Dusseldorf, said his train was diverted to Cologne.
Another passenger, Martin Sebastian Abel, said his train was stopped before it got to the main station and they were told there was an emergency. Police officers rushed to the scene, but they were not told what was going on, he said.
The station remained closed Friday.
In July, a Pakistani teen traveling on a train near Wuerzburg
injured five people with an ax before German police shot him dead. In a video found on YouTube after the attack, the teen described himself as a soldier of the caliphate and a martyr.
Police said he was driven by ISIS propaganda.