Sounds like a severe cat and owl shortage.
Maybe they got too large of an owl size, and they ate the cats.
Perhaps investing in twelve year olds and pellet guns would fix the problem.
Nearly every day for the past month, our wild cat has brought home (and eaten) either a mouse, chipmunk or red squirrel. Whoever kicked him out of their car and dropped him in our woods - Thank You! We love the guy.
A nearby feral cat colony has left us several dead squirrels on our driveway. Their way of thanking me for the kibble!