In the final scene, the flare gun goes from being on the ground next to JD to in his hand in the close up shot without his arm moving.
When JD and Turk read George's chart, it says he has ischemic bowel disease and JD's voiceover says that he is going to die. While IBD can be serious, it is treatable and is not the death sentence implied by JD. There would be no reason for them to think he was about to die, especially without a more thorough review of his medical history, which they did not do.