Cooper's Hawks can easily be mistaken for Sharp-shinned Hawks. Besides being larger in length, you'll notice their beaks are quite large. See them side-by-side on Who's Who in the Birds 101 section.
Cooper's Hawks feed on birds and small mammals just like the Sharp-shinned hawks; however, the Cooper's typically don't fly directly into the brush after small songbirds.
The Cooper's Hawk in the above photo hit a window. Even though it flew away a few minutes later, chances are it ended up having a broken neck.