(CNN)One person was killed and four injured in a stabbing attack Friday at a supermarket in Hamburg, Germany, police said.
Authorities identified the attacker as a 26-year-old man who was born in the United Arab Emirates, but they did not provide his name or citizenship status.
Police spokesman Timo Zill told local media the investigation was in its early stages and that no possible motive was being excluded, including terrorism.
He said the suspect was armed with a kitchen knife when he entered the supermarket and started stabbing customers. A 50-year-old man was killed in the attack, police said. Four others were injured inside the store before the suspect fled the scene and attacked a passerby, Zill said.
The injured include a 54-year-old woman and four men, ages 64, 57, 56 and 19. Some of the victims' wounds are severe, and they are being treated in local hospitals.
Witnesses followed the man and managed to restrain him until police arrived and arrested him.
Hamburg police tweeted that the suspect was "definitely a lone attacker."
The stabbing happened Friday afternoon local time at a supermarket in the Barmbek area to the north of the city. Hamburg is in northern Germany.