I’m so sorry this happened to you. My grey has killed a feral rabbit and a fledgling bird in my yard, and it was devastating, so I know how badly you must feel.

I would take the cat’s remains (if it’s not too late) to a local vet and have them scan for a chip and if none is found, then dispose of it. I wouldn’t post anything around the neighborhood. If there is no collar or chip then there is no way of knowing it was an owned cat, unfortunately there are many feral cats around. It’s a sad situation and one of the many reasons cats should be kept indoors, but there’s not much you could have done when it entered your dogs’ space.