Something that you're wrong about: he DIDN'T know that it was just a woman & two kids; he only saw the woman preparing to bathe at first, and the house & area would've indicated (albeit falsely, in this case), that she had a husband. Remember that he didn't find out the specifics until later. Also, he would've carried a gun in case he met anyone along the way, having had to walk through the forest to get to the house. Remember that he was a persued criminal who'd just broken out of prison (or a prison bus, to be exact). He didn't even meet Mookie until AFTER he left the house the 2nd time.
: )

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You mean when he went in the first time or when he went back? The first time I'm sure it was just to raid the house for some food/supplies and the second was to return what he took.
Sam is a thief but not a killer or a violent guy (Unless provoked like the bad guys trying to hurt her and the kids), they try to make that point with that scene and with him explaining how he went to jail later. I think he just pulled the gun Billy left him out as a reflex to the noise, just in case he needed to scare off some big guy trying to whop his ass so he could get away, haha.
Kristen Dowd
The Future of Independent Film

I understand the salt part (as I said that was accidental) but what was he doing in the first place? He wanted to attack Clyde?

Uh, he didn't pull the gun out until he heard noises (Mike walking around) upstairs. He had come to return the salt he borrowed the night before. Why do you think they showed him sitting the salt on the table before he bailed?
Kristen Dowd
The Future of Independent Film

I kinda thought he mighta been a rapist but that's just me.

i wondered that, i mean he saw her in the bathroom and was heading that way with his gun, what was he going to do if he hadnt heard the kid!