Classic 3am stuff, your dogs basically doing all the heavy lifting as an early warning system there mate.
Genuinely though the dog reaction is the bit that gets me every time with these stories, they pick up on something we just cant and they dont rationalise it away like we do. Did the figure move at all or just stand there? Because stationary is somehow way creepier than if it had legged it when the dogs started kicking off.
Also need to know - did you actually go outside or did you do the sensible thing and watch from behind the curtain like a normal person with functioning survival instincts. Asking for a friend (the friend is me, I would absolutely not have gone outside).
Anyone else had similar, dogs going mental at something in the garden that you couldnt properly explain? Feels like theres a pattern with these accounts.