But away from the books and high-rise digs, police believe he was a breakaway bikie, allegedly keeping a cache of firearms, moving large amounts of drugs and carrying out killings.

And in the past several months, he was under the covert watch of NSW Police.

Two weeks after allegedly murdering one of Sydney's notorious underworld figures – Pasquale Barbaro – Mr Sultani's life unravelled.

In dramatic scenes near his Australia Avenue apartment block on Tuesday, the Afghanistan-born 27-year-old was arrested as multiple investigations into the alleged murderer came to a head.

For the past 12 months, the gangs squad has been looking into the activities of Mr Sultani, who appeared to be living a double life studying a masters of business administration at Macquarie University and as an alleged career criminal.

That investigation, which included several other members of the Rebel OMCG's Burwood chapter, widened when the drug squad realised it too had Mr Sultani on its radar for suspected drug supply.

A few months ago, the homicide squad also joined in after Mr Sultani and his "crew" emerged as a potential suspects in some of its investigations.

He allegedly carried on his illegal activity, some of which police watched from afar in a covert and lengthy operation.

Court papers show that as far back as September, detectives suspected that Mr Sultani had been in possession of dozens of firearms.

He allegedly had 13, including nine pistols, on September 1 along with 2000 rounds of ammunition.

On September 22, he alleged had 11 guns at Mount Druitt and 7309 rounds of ammunition.

Mr Sultani was also allegedly involved in large-scale drug deals, including supplying two kilograms of methamphetamine in Olympic Park between August and his arrest this week.

He also allegedly supplied heroin and MDMA at different times around Sydney.

As police built up their case against him, tracking his whereabouts and recording his allegedly illicit deals, Mr Sultani allegedly committed murder.

He is accused of laying in wait outside construction industry figure George Alex's house on the night of November 17 for Mr Barbaro to walk outside.

Mr Barbaro was shot several times as he attempted to get into his Mercedes and died outside his friend Mr Alex's Earlwood home.

Fairfax Media has learned that police were monitoring the car Mr Sultani was in, which allegedly placed him at the scene of Mr Barbaro's shooting.

However, there was no intelligence to alert police to what was about to unfold.

It is understood the pair had a long-running history of animosity, something that wasn't unusual for Mr Barbaro, the son of a Mafia figure.

Mr Sultani was known to act as a "heavyweight" for hire but is also accused of carrying out criminal activities for his own reasons.

Despite not having a job or "any means to support himself" he had been stopped on numerous occasions with vast amounts of cash, according to court documents.

Interestingly he had also been old friends with Mr Alex, acting as a gofer for the construction industry figure in past years.

Police have said since Mr Barbaro's shooting that they don't believe Mr Alex was involved in the alleged murder.

Tuesday's arrests represented a colliding of worlds for NSW Police's State Crime Command, with three squads getting the chance to lay charges against him for allegations spanning over a year.

Mr Sultani is also charged with conspiring to murder former fellow Rebel bikie, Ricky Cianoat Wamberal in August, 2015.

It is understood he was also questioned following his arrest about three other gangland murders – the shooting of Rebels figure Michael Davey in March, Rebels Sydney chapter sergeant at arms Mark Easter in 2015 and Mehmet Yilmaz in September.

Those unsolved cases are four of eight that come under the umbrella of Strike Force Osprey, an investigation set up after Sydney's recent gangland shootings.

Eight other Rebels members and associates were also caught up in Tuesday's sting, in which 13 raids were rolled out across Sydney.

Three other people are charged with Mr Barbaro's murder, Siar Munshizada, a 28-year -old former Hunters Hill High School student, Mirwais Danishyar, 24, and Joshua Baines, 24.

Former St Patrick's College Strathfield student Jared Prakash, 24, was charged with participating in the criminal group.

Four other men, 22, 18, 27 and 29, were also arrested and charged with offences that were not for Mr Barbaro's murder.

They will all appear in court in coming months.

Strike Force Osprey so far has seized more than 40 mobile phones, 11 cars, a safe, cash and 43 guns.