Last week, police arrested Anthony Jamel Ellison for pistol whipping and robbing Tekashi 6ix9ine in July.

6ix9ine and his manager Shotti of Treway had previously suggested the robbery was an inside job, and now that's been confirmed by police sources.

The sources tell TMZ Ellison was part of the troll rapper's management team until he was fired after 6ix9ine's notorious LAX brawl.

Ellison was angry that he never got a fair share of the money 6ix9ine started making when his career took off. Police believe that that, and not so much the firing, was his motivation for catching and robbing 6ix9ine in Brooklyn. 

Police are still looking for another insider suspect who they believe was involved in the robbery and who had a similar motivation to commit crimes against 6ix9ine.

Ellison has been charged with one count of obstructing commerce by robbery and a count of carrying a firearm to commit a crime.