Passengers on the Kiel-Hamburg train were stabbed by a fellow traveler, killing two and injuring seven.

The assailant, a 33-year-old Palestinian man, was stopped and later arrested by officers at the Brokstedt train station in the northern German state of Schleswig-Holstein, police said.

According to a police spokesman, three of the seven victims were hospitalized in serious condition.

Home Secretary Nancy Fesser tweeted that she was “shocked” while expressing her condolences to the victims of the attack and their families.

The motives of the attacker have not been established, the German police are exploring all possibilities.

German authorities remain on high alert to prevent jihadist attacks, especially after the December 19, 2016 Christmas market massacre in Berlin. The Islamic State group claimed responsibility for the truck attack, which killed 12 people and injured dozens.

According to the country’s Interior Ministry, from 2013 to the end of 2021, the number of “dangerous” Islamists in Germany increased fivefold and reached 615 people. On a signal from the FBI, German authorities announced on January 8 that they had arrested two Iranians who allegedly planned a chemical attack.