I'm sorry for your losses Papabear. Redtails dont like owl's. You can use an owl decoy to disuade him from further hunting. His nature is to hunt but the owl decoy will make him pass on your pond & self preserve. He cant avoid his nature. The owl decoy can go on a post near your pond & if its within 15 or less feet away you should be ok.
Great Horned Owl's are fearless hunters & no hawk wishes to tangle with one.
see below for an example
http://wildbirdmart.com/wildbirdmart/rowl.html