Alistar pulverize bug

I was playing a ranked game on twisted treeline and the enemy team had an ad jg. I was playing jg and mid game his pulverize did 2014 damage. I am pretty sure this is a bug cause the only damage item I think he had was black cleaver, he also had 2 alter buffs and the Vilemaw buff.

If you can find this bug please fix it, I don't want to be half hit by an ad jg.