Tower didn't attack enemy after he killed me with smite

I was Irelia standing under my tower. I had low hp. Rek'Sai was standing under my tower, while it was attacking enemy minions. I started to attack him in hope he'll fight me and tower will attack him. He didn't attack me, just killed me with smite (blue sword) and moved away, he didn't flash, he just walked away amd tower didn't react (it countinued attacking minions).