I haven't seen my babygrrl kitty Sis for six days

I really think the same Folk's pitbull, who killed her brother, killed her, because those folks have been hiding from me, and stopped letting their dog loose in their yard, and have been walking it on a leash. It would escape sometimes. The last time I saw her, I tried to keep Sis in, but she howled til I let her out. She loved being free.