I had the same thing happen on one of my cichlid tanks a while back. I was medicating, so I threw in a powerhead to, like you did, get some extra surface turbulence and oxygenate the water. I came home from work the next day to 3, yes three, of my fish sucked up in the intake. It was a sad day. Needless to say, I pulled the powerhead, fish and all, and threw the mess into the trashcan.
Sad, sad days when you lose healthy fish.