First of all some information:
Champion, that I played: Nami
Enemy Champion: Veigar + (Shyvana and Ashe nearby, but not dealing any damage)
Veigar build: Rabadon's Deathcap, Athene's, Magicpen-Boots, Morello, Yellow-trinket
Ok, so the following happened:
Cait and me got ganked by a Shyvana on botlane while the enemy Veigar also roamed from midlane to us.
While Cait got focused I decided to run into the bot tower in order to get an execute.
Now Veigar has casted an E, that din't hit me...
At least I didn't get stunned nor have I been inside his 'circle'
The enemy veigar also ensured me via All-Chat , that he hasn't hit me.
Anyway, I died to him and Veigar got the kill.
The Death Recap says (besides turret dmg): "Event Horizon - Status effect"
So, the only explanation I can think of is, that I walked over the event horizon while it was building up. I don't think that the E should give a kill, while it is building up.
I have the following idea about how the bug happens: I remember, that a few patches ago Veigar's E came up instantly (I guess if was before the 6.9 patch). Maybe the game internal still thinks, that it rises instantly and thus even the non-loaded event horizon prevents an execute...
EDIT: I uploaded some screenshots at [Imgur](http://imgur.com/a/tCOG5), which make the whole issue clearer:
As you can see in the first picture, I have been standing on Veigar's E while it was building up. In my eyes, this shouldn't give a kill, as it doesn't really apply a Status effect, but I guess that's up to Riot.
In the second image you can clearly see, that I have been out of the E, when it was completely built up. I could also attach a replay file, if that's helpful.