After eventually climbing off the roof of the vehicle, Topai-Aveai – nicknamed "crazy" – ran into a public toilet before being detained but not arrested, according to the Courier Mail.
The Sharks player posted updates of the protests throughout the day before explaining what led to his outburst.
"Yes this is me. If you have any questions, shoot me a dm," he wrote on Facebook.
"Know the story behind the video, you didn't see the part where I bust a locked door open to escape so I could calm down, I weeped on my brother Jalen Reweti shoulder and had his beautiful partner Tupu there to help calm me.
"I am furious. I am angry. I am young. I am dumb. I am whatever you think I am.
"Most of all I am fed up of Police abusing their privilege to wear their uniform."
The Sharks listed player, who has yet to make his NRL debut, continued to speak out on social media as he posted the footage of himself grappling with the police car before climbing on top.
"This is for my brothers and sisters who have been oppressed for 100s of years by the White man. They've treated us like dogs for centuries, they've painted us with dirty brushes and they've created a system where only the white survive. Do your research mother f***ers," he wrote.
"If you are offended that I swear and miss the message ... you sir are apart of the f***en problem. I love Christ. He lives within me which makes me fearless to all men. Only God I fear.
"This was hurt and pain for my brothers and sisters who have had to suffer years of pain under the white law! THIS IS MY PROTEST AT A "PEACEFUL PROTEST" love it or leave it. I don't care. This is Me, this is the Cruz the system designed.
"They want to treat us and our beloved ancestors with cruelty and disrespect like we are caged animals ... I'll give you a caged animal."
Black Lives Matter protests across Australia have been largely peaceful but things took a turn for the worse in Sydney last night.
Dozens of protesters in Sydney's Central Station were hit with pepper spray last night after a tense stand-off with police officers.
In a statement, NSW Police said a man had been charged with offensive behaviour and resist police following the altercation just after 6pm last night.
"The 21-year-old was arrested and, after the group became increasingly aggressive, OC spray was deployed," police said.
