I do think there is someone else involved. To me the details we have leave unanswered questions. All speculation however.
I wondered that at first, also. It was such a ' successful ' crime, if I may put it that way. His record was mainly crimes that were not crimes against the person, yet here he is, straightaway in to a violent crime against a woman.
Sure , he may have knocked past 'girlfriends' around, but they didn't report it.
He doesn't look a leader, he probably wanted to be one, but obviously has missed that wild ambition by a country mile.
I don't think he would have an accomplice, or accomplices who could keep silent. Nor he , himself, if he had another person with him , he would deflect instantly.
He wasn't invisible around Greensborough/Bundoora/ Watsonia. He strutted the streets , with a certain impunity, he had no worries about skipping his court cases when it suited him, people appeared to know him ( " he lived on the 86 , he was always on that tram') but no one mentioned any sort of followers, in the gang sense.
The Senior Constable who had occasion to speak with him about missing his court date ( not a trivial matter ) didn't embed in him any sense of civil adjustment , 4 days before the murder.
That pic of him, the day AFTER the murder, him with his other hat, his second echelon hat ( because he discarded his first choice hat at the murder scene ) carefully placed backwards on his head, ( so cool ) and his smarmy little grin, and his subtle message about it ( Be4 an Afta , after what , pal ? ) portrays a young man who seriously thinks he got away with it, no one is ever going to connect him, he has outplayed them all, and we all better watch out in future.
The contrast between that pic, and the pic of him in the divvy car is huge , now he looks like a child caught in the headlights while playing on the street.