Police found evidence Tuesday that the suspect in a bloody Tokyo stabbing rampage purchased a small cache of knives just before the assault and reportedly posted despondent Internet messages warning he planned to kill people.

In one of the postings, he reportedly called himself "worse than trash."

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Tomohiro Kato, a 25-year-old factory worker, was handed over to the custody of the Tokyo prosecutors' office for further questioning into Sunday's attack, in which he allegedly slammed a rented truck into a crowd of pedestrians then jumped out and began a stabbing spree, killing seven.

Three people were killed by the impact of the truck, four died from stab wounds and another 10 were injured, police said. Kato, blood spattered on his face and clothes, was arrested on the spot.

It was the worst murder rampage in Tokyo in recent memory.

National broadcaster NHK showed surveillance tapes of the truck slamming into the crowd in the popular Akihabara shopping district, and of a man jumping out and running wildly among the panicked bystanders.

It also obtained surveillance footage of Kato purchasing hunting knives at an outdoor and camping shop two days before the attack. Kato is seen on the tape laughing with the salesman and at times making stabbing motions with his hands.

Police spokesmen who requested anonymity because the investigation is ongoing said Kato has at times broken down in tears during questioning, and has confessed to the crimes, but has been unapologetic.

Outside Tokyoe police, said Hiroyuki Kuwako of the Telecom Services Association.

Japanese media said the postings showed a very disturbed man raging against society and vowing to get revenge by unleashing his fury on the streets of Akihabara, a Mecca of electronic goods stores and a center of Japan's comic book and anime culture.

Akihabara was a high-profile target because its main street is closed to traffic on Sundays, allowing large crowds of pedestrians to flow into the area.

A chronicle of Kato's messages, carried by the Mainichi newspaper, portrayed a man who felt he had no future, was "ugly" and "worse than trash."

"Oh, I am hopeless," he wrote two days before the attack, according to The Asahi. "What I want to do: commit murder. My dream: to monopolize the tabloid TV shows."

Just 20 minutes before the attack, he posted his last message: "It's time."

No charges have been filed against Kato.

Under Japanese law, a suspect can be held by police for two days and then must be transferred to the custody of prosecutors, who have 20 days to either file charges or release the suspect.