THE HAGUE, Netherlands (AP) — Dutch police appealed for witnesses Friday as they investigated a stabbing in which one man was killed and another seriously wounded in the port city of Rotterdam.

A suspect was arrested after being overpowered Thursday night by members of the public and police. There was no immediate word on the motive for the attack, but police said Thursday night that witnesses reported the attacker shouting “Allahu akbar,” the Arabic phrase meaning God is great.

“It’s part of the investigation,” police spokesman Wessel Stolle said Wednesday night.

A 32-year-old man from Rotterdam was killed and a 33-year-old man from Switzerland was seriously wounded in the stabbing near the landmark Erasmus Bridge, police said in a statement. The suspect is a 22-year-old man from the central Dutch city of Amersfoort who reportedly attacked his victims with two large knives.

Police didn’t release the identities of the suspect or the victims of the stabbing, in line with Dutch privacy guidelines.

A sports instructor, Reniël Renato David Litecia, said that he hit the attacker with two sticks after seeing him attack somebody and managed to take the knives and throw them away.

He said he initially thought it was a fight, “but when I started running in that direction I saw that it wasn’t a fight. It was a man with two long knives who was stabbing another young guy and when I started shouting he turned around and started approaching everyone who was around him.”

Another police spokesperson, Kristel Arntz, said the assailant is believed to have attacked one person in an underground parking lot and then a second victim near a busy terrace near one end of the bridge that spans the New Maas river, which runs through Rotterdam.

Arntz also said that it was too early in the investigation to establish a motive.

“We have arrested a suspect, we are going to question him. We will look at all the witness statements and then we will look at what the possible motive was,” she said.