Story highlights Attacker was on radar for expressing jihadi views, German security officials say

Minister: Man was being monitored but was not considered a militant Islamist

Berlin (CNN) A man accused of a fatal stabbing in Hamburg, Germany, was known to investigators as an Islamist and was "psychologically unstable" but so far does not appear to have any terror links, authorities said Saturday.

The 26-year-old man grabbed a long kitchen knife at a supermarket Friday afternoon and stabbed three shoppers, killing one, before attacking four others on the street.

Eyewitnesses said he shouted, ''Allahu akbar,'' or God is greatest. Amateur video showed young men throwing chairs at the suspect to subdue him.

One of the injured was a Turkish man who helped others overpower the attacker, authorities said. Some of the injured were hurt seriously.

''We are shaken, horrified,'' Hamburg Interior Minister Andy Grote said at a Saturday news conference. He called it a ''barbaric'' attack and praised the citizens who overpowered the man as ''very courageous.''

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