Is this normal?
My ISFJ is WONDERFUL, but when something goes wrong and he's super frustrated (a piece of machinery doesn't work and he can't figure it out, over and over and over, for instance), he will let out a super big "GHAHHHHHH!!!" at no one in particular. Sometimes he's so mad he has to go outside and pace and yell a few times. No amount of consoling helps, it's best to just let him get it out.
It's not directed at me, it's not scary, it's just unusual. I've never heard anything like it.