Australian police have identified a 40-year-old man who suffered from mental illness as the perpetrator of a Sydney shopping center stabbing rampage that killed six people and left several more in critical condition.

New South Wales police Assistant Commissioner Anthony Cooke said Sunday the man had come from the northeast state of Queensland and was known to law enforcement.

"There is still to this point nothing that we have, no information we have received, no evidence we have recovered, no intelligence that we have gathered that would suggest that this was driven by any particular motivation, ideology or otherwise," said Cooke.