Tonight I was out late and watched what I’ll call an escort plane with its normal lights on, two helicopters with absolutely no lights on flying in line behind it, and at the very back of the formation was another plane with its lights on.

Three hours later, just about ten minutes ago, I woke up to the loudest and lowest sounding helicopters I’ve ever heard, and certainly never have heard late at night. They sounded a lot like the ones that were flying in darkness between two planes, but just much lower.

Would they likely have been Apaches? The rotary sound was deep, loud, and powerful. Not like a normal helicopter we’d normally see in our area.

Im an absolute newbie to aviation identification but I’m interested in what they could have been? Thanks for humoring me

Washington State