Oliver Stark wasn't initially sold on his character Evan "Buck" Buckley's big 9-1-1 season 9 finale twist ending. Warning: Spoilers below for the 9-1-1 season 9 finale. During the final moments of the Thursday, May 7, episode, titled "Hearts and Flowers," it was revealed that Buck signed paperwork making him the legal guardian of 4-year-old Theo after his parents, who utilized Buck as a sperm donor, both died in a tragic accident. "I was pretty apprehensive," Stark, 34, admitted while exclusively speaking with Us Weekly about the finale.