It's not "aggression"...it's "self-defense"...he was afraid. Snakes don't see well, & a figure coming toward them that they cannot identify thru either scent or
touch (they do not recognize us visually) suggests a predator heading toward them. Since even captive-bred snakes are still "wild" animals (relying on their
instincts) your snake acted in survival mode. Try to remember to identify yourself when approaching using scent &/or touch and you'll have a calmer pet.
It's not a "problem"...his reaction was normal snake behavior.