this took place inside the mall.
Umm, ah, check the video again. It happens outside the store, in the open air.
Bodily harm? Assault and Battery? You might want to look up legal definition on that part. I see no such thing in this case. I see a legal detainment by security guard. Depending on state - there is a liability protection for security guard. Since this took place in California....
A choke hold is causing bodily harm. Tackling someone from behind and using any type of force with intent to restrain or injure is assault and battery. Why is this not clear to you? It's clear to everyone else.
Best Buy's policy prohibits the employee from handling security-related issue. That's why the store hires security guard for that purpose. For greater legal protection - they hire specialized security guards - "Loss Prevention"
You might want to check into that a bit more closely. Their policy covers ALL EMPLOYEES, including security. They do not initiate physical confrontation. Instead, they use surveillance and witness to press charges after the suspect is gone.