Complex sentence: As they all head back to the beach they witness the sound of gunshots and a woman screaming and then they see two men holding a woman hostage with a bag over her head after just killing her male companion.
Split into simpler sentences: As they all head back to the beach they hear the sound of gunshots and a woman screaming. Approaching the source of the commotion they see two men holding a woman hostage with a bag over her head after just killing her male companion.