George MacKay

 portrayed Bill Turcotte, a young man who helps Jake spy on Lee Harvey Oswald.

Biography
George MacKay is an English actor best known for his roles in "The Boys Are Back" (2009), "How I Live Now" (2013), "Sunshine on Leith" (2013), "For Those in Peril" (2013), "Captain Fantastic" (2016), and "Ophelia" (2018).