Transcript for Terrifying attack on holiday shoppers in Melbourne called 'a deliberate act'

We turn next overseas to the terrifying attack on holiday hospit shoppers. An SUV used as a weapon on the streets of Melbourne, Australia. A trail of injured people left behind. Tonight, police are calling it a, quote, deliberate act, but so far, not terrorism. ABC's James Longman tonight on the investigation. Reporter: Frenzied chaos on a busy Australian street. This mangled wreck, the weapon in what authorities are calling a deliberate act. Witnesses say the white SUV ran red lights and veered onto those rail lines, before slamming into pedestrians. There were people screaming, running separate directions thinking it was a bomb. Reporter: Injuring 18, one still in critical condition tonight. This man dragged from the SUV, officers seen holding him down and slapping him. Authorities saying there is so far no link to terrorism, but the suspect was known to police. He's a 32-year-old Australian citizen of Afghan descent and has a history of drug use, as well as mental health issues. Reporter: A similar incident in January killed six people right around the corner. It's shocking and surprising that it happened again. Reporter: Concrete blocks were installed to prevent more vehicle attacks, but tonight, Melbourne is shaken, again. Tonight, the suspect is still in the hospital, where police are yet to formally interview him. They're still looking for a motive for this latest vehicle attack. David? James Longman tonight.

This transcript has been automatically generated and may not be 100% accurate.