As a starting point, that does *not* mean he ultimately won't be charged by the Feds or face additional state charges.
The video alone likely gives prosecutors enough to argue for a third-degree murder conviction.
They are difficult to investigate, and juries can give them the benefit of the doubt for acting in the heat of the moment.
The Feds can also separately indict him, which would mean he would face criminal charges in two courts.
That is a very high bar to meet in any case.
That said, the inadequacy of the letter of the law is only one obstacle to successfully prosecuting officers.