Complex sentence: Nate jumps onto the train and fights through it to find Chloe, who refuses to join him as he compromised them earlier, before Flynn arrives and shoots Nate in the abdomen.
Split into simpler sentences: Nate jumps onto the train and fights through it to find Chloe, who refuses to join Nate as he compromised them earlier. As the two argue, Flynn arrives and shoots Nate in the abdomen.