Iron Golems are summoned in players' face when Villagers need help

The Bug

2day I was trying to cure a Zombie Villager near a group of Villagers. I was about curing whom, while a wild Iron Golem appeared all of a sudden IN MY FACE, and, of course, who killed that Zombie Villager.

How to Produce?

Summon which can attack Villagers nearby, wait 4 a while.

PS

That really made me confused when a telegraph pole (XD) suddenly appears in my face.