Who'd have thought a random vampire attack would be helpful? I'd just finished talking to him about entering the house when a Master Vampire and two Death Hounds showed up and killed him. It flashed up, "Failed: House of Horrors." Tyranus was the only person who died before the undead were dealt with. Now I don't have to start that damn quest just to get him to stop pestering me to help him. I thought he was essential until you were inside but looks like I was wrong. Abandoned house will stay locked and abandoned forever. Best random vampire attack ever.

Lucky for you. I normally just avoid him.

I'm kind of jealous. I wonder if I hang out around Makarth and keep re-entering the city after dark if I could get the same wonderful results? Guess I'm off to the City of Blood and Silver to find out.

He shouldn't be killable until after finishing "The House of Horrors," at least according to the http://www.uesp.net/wiki/Skyrim:Vigilant_Tyranus, which is known to be incorrect from time to time. If I had to guess, perhaps this was a rare bug, but I don't know if mods (if you play on PC) or some change with the 1.9 patch could be a factor.

Oh man if it wasn't for that idiot, constantly bombarding you with "have you seen anyone come in and out of this place" even after being told by someone it's abandoned, that quest could have been cool. It's about as annoying as that dude who gives us that stupid note he claiming we dropped to start Madanach quest. - _ -

I agree about both of those. Brynjolf's line bugging you about "not earning all that coin your carrying" is just as bad though.

I play on Xbox 360. It would have to be during House of Horrors. If I had made it inside the house with him he would have eventually turned hostile and the only way I could leave would be killing him and then listening to Molag Bal. It must be as soon as House of Horrors starts he looses his essential tag. He turned to unlock the door having become non essential just as the vampire attack began. Thankfully he didn't survive the attack.

The coward was a disgrace to the Vigilant anyway, Molag Bal tells him to kill and he turns to attack the person who was trying to help him instead of offering to work together to try to escape. But I won't need to go through all that now. He died and the house will remain locked.

Terrible quest design.

It would have to be right after you started the quest because he's essential until the quest starts and he moves towards entering the abandoned house. I know he's essential before hand because I nearly screwed myself out of that quest by killing the Vigilents at Stendar's beacon and the hall of the vigilent (Happened before Dawnguard came out) and then he kept attacking me. Thankfully I was able to get around that by knocking him out and then going into sneak and quickly rising up and talking to him before he went aggro again.