I'm pretty sure this was a juvenile Cooper's hawk because:
it flew right over me and it seemed very large both then and when perched
there are a pair that nest regularly in the Rattray where it was seen
it just didn't seem like a Sharpie
However, before I mis-report to eBird, what do others think?
[attachment=0:3f0ns28x]CooperSharpTail.jpg[/attachment:3f0ns28x]