Is our Hen Actually a Rooster?

We’re complete chicken newbies, but we were totally convinced that our Rhode Island white was a rooster. We got our chickens when they were chicks at Easter so they are about 4 months old. Our white chicken, Kevin, tries to get out, makes a bit of noise and is defensive/protective. It does this squat/shuffle when you get near it and will peck at us. It also seems to have slightly larger comb and wattles than our other 3 chickens.
We did not want a rooster! So we were worried about him. Check out the video to find out if Kevin is a rooster and how we finally found out!