Fish moved to prepared foods will still eat live foods at any given time. In fact, they relish live foods if they're mostly on prepared...in my experience (and I have a lot of it, not to toot my horn).
Also, crays kill and maim even if they're well fed. At night they grab sleeping fish... it's just in their nature. My neighbors set up their first fish tank, a 29 with a couple of dogtooth cichlids, then they decided to buy two small crays. A couple of days later their cichlids completely vanished. They found the bodies in a cave, half decomposed.
Besides, this is your larger crappie, right?
This is going to sound a little "out there" but in my experience, fish in this condition aren't up for beating up other fish.
Also, that cray you have there isn't exactly a small cray.
So, I'd blame the cray.