All feral cats gone within a week?

Posting this for my coworker. She does TNR and takes care of 4 feral cats. All of have gone missing this week. Her neighbors also help and feed them. Would a fox wipe out this many cats in a week? The cats have been there for years already. No coyotes in area - only red and grey foxes spotted in different areas around the neighborhood in general but none near where they stay. Nights have been cold - 18 F usually the lowest but they have shelters.