Caroline
#1...what did she inject Patrick with?
#2...why didn't she drink the kool-aid instead of lighting herself on fire????
Can't really answer #1. I don't think it's specified in the movie, but I'd assume it's the same poison that was mixed in with the Kool-Aid.
As for #2: "Father" specifically instructs Caroline to keep filming during the final ordeal. She does so until most of the cult members are dead, then proceeds to kill her brother and herself.