Wasn't sledge that shot the dude that panicked out of his hole, not sure he was even deployed yet

Maybe if the marine had called out and alerted people that he was crawling out of the hole, he wouldn't have been shot.
IF he had called out, he would have pinpointed himself to the Japanese attempting to infiltrate the line; 'rock & hard place' moment it seems.
Why can't you wretched prey creatures understand that the Universe doesn't owe you anything!?

I am familiar with the concept of not getting out of one's position and using challenge/passwords but thanks for explaining the scene to me. I have Xfinity and no DVR so it's hard for me to go back and examine the scene. I couldn't tell if it was only a friendly fire episode or a Japanese attack coupled with one. I appreciate you laying that out for me.

Basically, when soldiers are hunkered down in fox holes, the soldiers that are on watch are supposed to be extremely vigilant and shoot anything that moves.
One of the scenes is where Sledge is on watch, and he barely sees a couple japanese soldiers jump into a fox hole then stab the marines sleeping inside. One of the marines survives the stealth sneak attack and crawls out of the foxhole only to get shot by Sledge because Sledge thought he was a japanese soldier.
You're never supposed to get out of the fox hole where you're supposed to sleep, not even to go to the bathroom because you're likely to be friendly fired by the soldiers on watch.
Maybe if the marine had called out and alerted people that he was crawling out of the hole, he wouldn't have been shot.