Yes, he is a mix of some sort. As far as aggression goes, individual personality is a lot more important than breed. Just keep an eye out and see how it goes.
Roosters get aggressive by how they are raised. If you offer a foot to fight, or hit them with brooms they can become aggressive.
My roosters get picked up if they ever come near me. Soon they learn to not come near me, or get picked up if they do. Some like being picked up. You may have a rooster that is naturally more aggressive. Rehome them or freezer camp the mean ones. Never show fear or be timid, and always keep your eye on them if they come around.