It is one of the many duties of the FBI to investigate assaults on Border Patrol agents. Its one of several investigations the agents will have to go through
If the FBI were investigating to ensure BPs rights weren’t violated I’d be OK with that, but, living on the border, it’s painfully clear, the only “rights” being investigated and protected are those of the illegals.
For good or for ill, the FBI has investigation responsibility on Indian reservations.