Give it some time. From what I hear Novak was not in that particular Audi and it was someone else unrelated driving out of the building. The supporters pepper-sprayed was a direct result of reactionary anger to the tweets that said he was arrested and to the presence of the black Audi that was escorted by police. Later on Novak's supporters calmed down and were seen in a celebratory mood on Federation Square.

Please also keep in mind that Aussie Cossack is based in Sydney and not Melbourne, so his sources are more removed from the location than is ideal.

So far no one has confirmed that he was arrested at all and on the contrary say he wasn't arrested. For some perspective, Real Rukshan at first said Novak was arrested but corrected his statements upon his own investigation of what really happened, and posted the following:

FB https://www.facebook.com/therealrukshan/posts/369269021671208

Update: Reports of Novak's arrests attributed to his father have been shutdown by the Federal Government and Tennis Authorities as a decision has not yet been made on his deportation by the Minister responsible.

Novak Arrested according to comments attributed to Novak's father by reporter Ksenija Pavlovic McAteer.

Australian Government arrests Novak after Australian Federal Court rules in his favour. The tennis player was found to have met the requirements to have entered Australia according to a Federal judge just prior to his arrest.

Is the Federal Government being vindictive after losing in its own Federal court? The worlds focus is now on Australia as it looks like we are about to make an example of an individual not because he broke rules but because it is inconvenient for the Government to have him in the country.

FB https://www.facebook.com/therealrukshan/posts/369173255014118

Update: Reports are that Novak is free to leave his lawyers office as Australian Government officials decline to use powers to deport him at this time. Did the international spotlight unravel the Government or is there more to come?

Updating the previous post as well, this is the quote attributed to Novak's family fuelling speculation of an arrest.

“Autocracy has shown its true face today. Contrary to the decision of the Independent Court of Australia, dictator Scott ordered the arrest of my son, Your World Champion, Novak Djokovic, and deportation, banning him from entering the country for three long years." Srđan Đoković

There is still uncertainty because the Federal Government is indeed being vindictive, by keeping the threat of exercising personal power over Novak Djokovic's head, AND not confirming or denying if they'll even use it. That sort of pressure would make anyone nervous, but I trust that Novak will remain strong.