A way too-low flying purple martin drowned in my pond today. I didn't see the crash happen, but one of the LMB was tuggin at the dead bird, pulling the carcass under repeatedly, in mimicked discovery channel shark-attack style. It was finally pulled under never to resurface.
I've heard of LMB and other big pred fish eating birds, but was surprised at this behavior.

Sorry...no photos or videos to back up my claim.