UPDATE: Numan Haider 'wasn't conspiring with others to ambush police'

Police don't believe Melbourne terror suspect Numan Haider was conspiring with others to ambush police.

Deputy Commissioner Graham Ashton said there were some young males in Haider's presence before he attacked two officers and was then fatally shot on Tuesday night.

But police said it was a "moving" investigation and it was not their theory that there was a conspiracy to ambush the officers.

"We haven't ruled anything in or out," Mr Ashton said.

"It's not our prevailing theory this was an ambush."

Mr Ashton said Australian Federal Police were looking into whether Haider searched for Prime Minister Tony Abbott's next visit to Melbourne and his movements.

He said he could not confirm or deny if that had happened, but said the AFP did not have any specific information about threats to Mr Abbott.

It's too early in the investigation to rule out further arrests, he said.

Mr Ashton said Haider's family were in shock and had been co-operating and will continue to co-operate with police.

They also wanted answers as to why the 18-year-old became radicalised, he said.

Mr Ashton said the investigation, expected to go on for months, will focus on what motivated Haider.

"Over the coming days and weeks we will talk to many people to find out what motivated him," he said.

Earlier it was reported the 18-year-old was with up to three men when he asked two counter-terrorism officers to meet him at a Hungry Jack's restaurant on Tuesday night.

The officers rejected this proposed meeting spot and instead agreed to meet outside a police station in Endeavour Hills, where Haider was killed after allegedly stabbing both officers.