A German prosecutor says an 18-year-old who stormed his school armed with an ax, knives and Molotov cocktails in an attack that injured nine people had marked the date in his calendar with the word "apocalypse."

Ansbach State Prosecutor Juergen Krach said the teen remained hospitalized Friday and could not be questioned, but a search of his home turned up the calendar on which he had marked Sept. 17 and a handwritten will.

Krach told the Associated Press that the will was "dated shortly before the attack," adding that the teenager's motive remains unclear. Reports that the attacker was in psychological treatment still need to be verified, "but that can be assumed," Krach said.

Police have questioned the student's parents, he said.

The teenager, whose name has not been released because of German privacy laws, injured eight fellow students and a teacher just after classes started at 8:30 a.m. Thursday morning. Police responding to a student's emergency call shot the attacker in a hallway.

The injured teacher and six pupils suffered burns after the attacker lit a Molotov cocktail and threw it into an 11th grade classroom, police said, but none of their injuries was life-threatening. A female 10th grade student who was struck on the head with the ax is still in critical condition. Another female student was treated for second-degree burns and smoke inhalation.

Some 700 students fled the Carolinum high school, a nearly 500-year-old institution on the cobbled streets of Ansbach, Bavaria.

Police said it is not clear if the attacker, who had no police record, purposely selected his victims.

The attacker was shot five times in the upper body during his arrest, 11 minutes after police responded to a call from a student who smelled smoke and activated the fire alarm. Many pupils thought it was a routine fire drill and only learned later what had happened.

Doctors plan to bring the teen out of a medically induced coma on Friday. Krach said prosecutors do not expect to question him immediately, but will execute their warrant on charges of attempted murder.

It was the latest in a series of violent attacks on schools in Germany in the past decade and the second this year.

In March, 17-year-old Tim Kretschmer fatally shot 12 people at his former school in the southwestern town of Winnenden. He fled the building and killed three more people before turning the gun on himself.

Teacher and police union leaders said the attacks showed that more counselors and better monitoring systems are needed to prevent such incidents.

"At least one social worker and one psychologist belong in every school in Germany," Rainer Wendt, leader of a major German police union, told the Neue Osnabruecker Zeitung newspaper.