Forum:YMIR Gone Nuclear?

I was playing earlier on the Neith mission http://masseffect.wikia.com/index.php?title=Special:Interstitial&u=%2Fwiki%2FN7%3A_Wrecked_Merchant_Freighter and was killed due to a YMIR Mech going all out Nuclear on me, similar to the Cain but bigger. Has anyone else ever had this happen or was this a random event?