A Palestinian man who allegedly stabbed one person to death and wounded six others in Hamburg was known to authorities as a suspected Islamic radical but also was psychologically unstable, German officials said Saturday.

The suspect, a 26-year-old who had no identity papers other than a birth certificate showing he was born in the United Arab Emirates, was quickly overwhelmed by passers-by and arrested after Friday's attack at a supermarket in Hamburg's Barmbek district.

He was not named by authorities in keeping with Germany privacy laws.

The man's motive remained unclear Saturday, but he is believed to have acted alone and there are no indications he had links to any network, Hamburg state interior minister Andy Grote said.

Police said the suspect grabbed a kitchen knife with a 20-centimeter (nearly eight-inch) blade from a supermarket shelf on Friday afternoon and stabbed three men, one of them fatally. He then left the supermarket and hurt another three people outside, not all of them with the knife. Passers-by then pursued and overwhelmed the suspect, who was arrested by police.

Grote said none of the wounded was being treated for injuries considered life-threatening Saturday, though some were seriously hurt.

The man arrived in Germany in March 2015 after stops in Spain, Sweden and Norway. His asylum request was rejected late last year and authorities were trying to secure new Palestinian papers to deport him — a process in which they said he had cooperated.

Officials said he was on their radar as a suspected Islamic radical, but not as a "jihadist."

A friend had tipped authorities off to changes in the man, telling them that he stopped drinking alcohol and started talking about the Quran, Torsten Voss, head of the Hamburg branch of the domestic intelligence agency, said.

Officials interviewed the man and came away with the impression that he was a "destabilized personality" but not someone who posed an immediate danger, Voss said.

"We evaluated him rather as someone who was psychologically unstable than had clear Islamic extremist motivations," Voss said at a news conference. Authorities don't know of any connections to Hamburg's Islamic extremist scene.

A search of the man's room at a center for asylum-seekers turned up no weapons or weapon-like objects, prosecutors said.

The suspect hasn't yet talked about Friday's attack, prosecutor Joerg Froehlich said, though he has indicated that he acted alone.

Froehlich said authorities intend to ask that he be held in custody on suspicion of murder and five counts of attempted murder, but may seek to have him held at a psychiatric unit instead.