Turret Aggro Priority Question

I was playing kled and was fighting a riven under turret. I still had Skaarl and then i killed riven, after that i took a tower hit that made me lose skaarl but i did not lose tower aggro even though there were plenty of minions. I tested it later in the practice tool but i would never keep aggro when i lost my mount even if i was closer to the turret than the minions. How does it even work? Is there somewhere i can look this up cause i tried lolwiki and browsed the boards and didnt find anything.

plz send help