You've got deer
Some of the mating calls of deer can be really bloodcurdling.
Also a deer at the window would fit the silhouette. Deer are curious critters.
Other critters that make horrible noises at night: foxes, they make a really wide range of weird and horrible noises, apparently so do badgers.
But the worst noise I ever heard was a sika deer in my local woods.
Was walking the dogs, at that time it was Bilbo and Phoenix. Bilbo was the most fearless dog we've ever owned.
Nothing phased him: loved bangs, fireworks, popped balloons. The louder the nouise the more he liked it.
Phoenix was a wimp, didn't expect her to come with me - but Bilbo should have backed me up
It was dusk and we were in the woods. There was this truly horrible scream, sounded like someone being skinned alive.
The dogs both froze, leaving muggins to go look on my own. And I wasn't all that happy about it.
It's the only time in his life I ever saw Bilbo nervous about a noise.
I've spent the last 35 years knowing the most dangerous thing in the woods at night is me. That night is the only time I ever had any doubts about it, lol
As i got into the undergrowth an animal did bolt about 20 yards away.
Turned out it was a passing sika deer. I say passing as I've not heard it since or before.
Listen to that with your eyes closed and then imagine hearing it, at night, in woodland.
Yeah - scares the crap out of you