Trains are not stopping at the station.
It is unclear how many passengers were injured in the attack, though several victims were reportedly found bleeding out on the the ground after the suspect assaulted a train.
The motive for the rampage wasn't immediately clear, but the incident sparked chaos at the station in Dusseldorf, a city of about 594,000 in western Germany.
Police were still looking for other possible suspects, a spokesman for the German federal police said.
"There was blood everywhere", the agent said. He was unable to say how serious their injuries were.
The zoo has remained closed since Gustavito's death, and authorities are investigating, the BBC reported.
Germany suffered a terror attack in Berlin in December past year when a lorry ploughed into a Christmas market, killing 12 and injuring 56.