Teran shot a state trooper immediately before he was shot. I'd say his shooting was justified.
Law enforcement in the US (and many other countries, including others where environmental protesters are often killed) has been know and documented to lie routinely, so is not a reliable source to take on face value.
A bullet from his gun was found in the state trooper's abdomen, and I find it extremely hard to believe that Teran shot a state trooper after being shot multiple times, especially given cops' tendencies to shoot until a target stops moving.