Great capture. I'm also leaning towards Cooper's Hawk, however I can't say 100%. It can be very tricky IDing accipiters from a single picture. I feel much more comfortable if I am able to observe the bird in person.
Just to let you know how hard it can be, this is taken right out of the Peterson's Advanced Birding Guide
"The need for caution:
As recently as the late 1970's some ornithologists were still insisting that accipiters could not be identified in the field, because it appeared that each well-known field mark was subject to variations or exceptions. This extreme view has been altered by further study of identification but the need for caution is still apparent. Accipiters can be named with confidence only if several different field marks are seen well. No single field mark is fool proof by itself. No expert can name every bird seen - some views of accipiters are just too brief or too distant. The real expert knows when to say "I don't know."
The value of experience:
Use of shape and flight style (adding up to the "jizz" , or "gestalt" ) As field marks demands some comparative experience. If you can get to one of those favored spots on a coast, lakeshore, or ridge where raptors concentrate in migration, study as many accipiters as you can, constantly analyzing and refining your impressions. But when you try to use these characters elsewhere, remember that the surroundings can have an effect."
