Travis McMichael (the one who had the actual fight with Arbery) has never been a police officer.
His father Gregory McMichael, who was standing in the back of the truck the entire time, was a police officer until 2019. His law enforcement certification along with his powers of arrest were suspended and his service firearm was taken away from him in February 2019. He retired while still under suspension in June 2019.
At the time of the encounter with Arbery, he was a civilian with no powers of arrest beyond that of a civilian. And at no time did he physically engage with Arbery. In fact, Gregory McMichael was on his phone in the back of the truck until after Arbery was shot.
Were you there? If not you may know beyond what you thought you saw in a video.