This is an immature White-tailed Hawk. This species is fairly unusual this far NE up the Texas coast, but they are seen here occasionally. Note the all dark head and white chest (the white on the chest is variable in size from individual to individual). Dark belly and solid dark back. Note wings are longer than the tail which does not occur in Red-tailed Hawk. Note whitish gray tail with blurry dark tail band as well as rufous patch starting to show at shoulder and note white rump area in flight. This is a plumage not familiar to many birders but it is a very attractive hawk. Today was dark and cloudy but I got the best shots I could.

Also see:
http://www.inaturalist.org/observations/480854
for a bird in similar plumage I photographed the next day.