I have a friend at work who is quite a birder, and he agreed that it was very possible that an owl could take a kitten, and then weirdly enough, I was relating this to another guy on our block - on the other diagonal corner, and he said that he has seen it happen. An owl swooped down and took a half-grown kitten.
The plot continues to thicken. Our neighbor, right to the east of us, left a little dog out doors list spring for 30 minutes or so and it vanished as if plucked off the face of the earth. Never to been seen again in spite of extensive door-to-door canvassing of the neighborhood, and many, many lost dog posters put up all over the city.
You are right, it might not have been an owl. But it does make you think.
In addition to owls we also have hawks, doves, and in the spring and fall about 7-10 vultures that live in these trees.