I concede it is possible it might be an adolescent red-tail...the feather patterns on the dark feathers do look very, very similar. Here is a comparison image I made:
I also saw this description: Most Red-tailed Hawks are rich brown above and pale below, with a streaked belly and, on the wing underside, a dark bar between shoulder and wrist. The tail is usually pale below and cinnamon-red above, though in young birds it’s brown and banded. “Dark-morph” birds are all chocolate-brown with a warm red tail. “Rufous-morph” birds are reddish-brown on the chest with a dark belly.
By this it seems there is wide variation in the irregular dark pattern marks, and I have heard the tail doesn't always have to be that red.