I have no idea what US QRA RoE are but I would guess they would probably look to get pretty close before shooting.
If there is a requirement to visually identify the aircraft, that can be done from a few miles away with a pod (didn’t see a pod on the PDX F15s, although that doesn’t mean they weren’t carrying one).
The videos that have been released appear to support my suggestion that the F15s would want (at least one of them) to get close.
You have probably read reports before of fighters reporting what is going on in the cockpit of airliners. That might give you an idea of what their job might entail. Admittedly, it would have been very hard to close to that sort of range in this case.
If the order to fire came, they had a choice of AMRAAM or AIM9. I couldn’t possibly discuss what range that would be from but once again, Wikipedia might give you a good idea. Remember, the jet you see in the video wouldn’t necessarily be the guy who fires the shot if the call came.
Anyway, it’s a very sad story regardless.
BV