There's been no official reason given for why Claudette was killed off 9-1-1, but there may not need to be. The whole franchise is known for its willingness to kill off characters, and since Claudette particularly served as an antagonistic foil (especially for May), her patching things up with May meant the character had run her course.

Williams' departure hadn't been announced or hinted at prior to "May Day" airing, so it's less likely that the actress wanted to leave and more probable that her character arc had simply played itself out. Whatever happened, Claudette deserved a better send-off than the brush-off she got from Jonah. Hopefully May will give Claudette her due respect in the next episode.

9-1-1 airs on Mondays at 8 p.m. EST on Fox.