Investigators found a hand-painted ISIS flag in the room of the 17-year-old asylum seeker who wounded four in an ax attack on a German train, an official said Tuesday.
The incident Monday night took place on a train near Wuerzburg-Heidingsfeld, about 70 miles southeast of Frankfurt. The Afghan teen was shot dead by a SWAT-style team after the attack.
Bavaria's interior minister Joachim Herrmann said the teen — who came to Germany over a year ago as an unaccompanied minor and had lived with a foster family for about two weeks — appeared to have acted alone.
He told a press conference that the handpainted ISIS flag was found in the teen's room along with texts discussing the life of Muslims and how they "have to stand up and fight." A note found also suggested the teen may have written a farewell letter, Herrmann added.
The ISIS-affiliated Amaq Agency released a video that it claims showed the attacker saying he was about to carry out a "martyrdom operation in Germany." A statement from the agency did not indicate whether ISIS had any role in directing or organizing the attack.
Herrmann, however, said the motive for the attack still needed to be investigated and that authorities were trying to find out more about about the suspect's background and route to Germany.
"I cannot say if this is the result of a network," he told the press conference.
Earlier, Herrmann told ZDF Television that investigators were looking into reports the attacker shouted "Allahu akbar" — "God is great" — during the rampage.
Four Hong Kong citizens were among the injured, according to the Hong Kong immigration department. Two of the injuries were reportedly serious.
Between 10 and 20 people sustained light injuries — but the majority of those were suffering from shock, police said Monday.
Monday's attack comes days after a driver rammed a truck into a crowd in Nice, France, at the end of a Bastille Day fireworks show, killing 84 people. Authorities in France have called that attack an act of terrorism.
In Germany in May, a man armed with a knife killed one person and injured three others in a dawn attack on a train station near Munich. The attacker in that case was arrested.
Germany last year registered more than 1 million asylum seekers entering the country, including more than 150,000 Afghans.