If it's a night terror, it will happen in the first few hours of sleep, my dd usually has then when we're still awake or right about when we go to bed. She screams and thrashes around, but her eyes are closed and she's nearly impossible to wake up. With night terrors, they don't know what's going on, so it's actually worse to pick them up as it just freaks them out more on the subconscious level. Horrible for mom and dad though b/c we just want to give hugs and make the crying/screaming stop. We'll take dd and put her on our bed so I can lay close to her without holding her. Sometimes she'll wake up after she comes out of it and need some cuddles, sometimes she'll just fall back into deeper sleep. They tend to happen when overstimulating/overexciting things happen or when she's short of sleep from a weird day (we had a bunch around the 2-1 nap switch and some more recently as she doesn't always nap).
With SA, he'd actually be awake and looking for you, chances are he'll calm down when you get to him.
HTH!