Complex sentence: The three remaining crew members then agree to arm the "Nostromo"' s self-destruct mechanism and escape in the shuttle, but while gathering the required stasis coolant, Parker and Lambert are ambushed and killed by the Alien.
Split into simpler sentences: The three remaining crew members then agree to arm the "Nostromo"' s self-destruct mechanism and escape in the shuttle. While gathering the required stasis coolant, Parker and Lambert are ambushed and killed by the Alien.