Police say an investigation into what radicalised Melbourne teenager Numan Haider is expected to take months.

What turned a Melbourne teenager from a good family boy into a terror suspect will be the focus of a police probe expected to take months.

A crowd gathered at an Afghan mosque in outer Melbourne on Friday to mourn Numan Haider, who was shot after stabbing two police officers outside Endeavour Hills police station on Tuesday night.

A police investigation, expected to take months, will focus on what motivated the 18-year-old.

Victoria Police deputy commissioner Graham Ashton said Haider was with some males just before the incident but this did not suggest there was a conspiracy to ambush the two officers.

“Certainly that’s not our prevailing theory at the moment,” he said on Friday.

But it is too early to rule out further arrests, he said.

Mr Ashton said Australian Federal Police were also looking into whether Haider researched Prime Minister Tony Abbott’s movements although the AFP did not have any “specific” information about potential threats to Mr Abbott.

One of the injured officers has left hospital, the other needs more treatment.

Mr Ashton said both officers are devastated Haider was dead.

Other officers had visited the property of an associate of Haider on the day of the incident but he rejected claims that house was ransacked.

Haider came from a good family who were co-operating with police and they too wanted answers about what led him to attack the officers.

“They are very shocked obviously by what’s happened, deeply saddened and shocked at the death of their son,” Mr Ashton said.

“They particularly want answers as to how he has become radicalised to the point he has done this act.”

One of many avenues police will probe is the Al Furqan Islamic Information Centre, which said on Thursday it is in no way connected to Tuesday’s incident.

Islamic Council of Victoria secretary Ghaith Krayem said on Wednesday Haider had in the past been involved with Al Furqan, which was raided by police in 2012 but he hadn’t had recent contact with the group.

The incident has led to reports of Muslims being abused and threatened, with chief commissioner Ken Lay urging people to report any incidents to police.

Police statistics did not show a spike in abuse of Muslims.

Sheikh Abdul Azim, president of the Australian National Imams Council, said Tuesday’s incident was “a wake-up call for everyone”.

“We are calling for people to calm down, just take it easy,” he said.

“When you see a Muslim man or woman, it doesn’t mean that he’s your enemy.”

Police say counter-terrorism officers had been aware of Haider for about three months and had invited him to the police station after becoming concerned about his behaviour.

Haider’s passport was cancelled on security grounds last week and he had been seen with an ISIS flag at a Melbourne shopping centre.