It doesn't make any sense. I thought that the "Butcher" only killed certain people, namely women. I've recently discovered three bodies, two of them men. One was that male beggar, one was that captain guy, and the last was my contact for the Thieves Guild! I couldn't believe it. Also, it was apparently all within the same night, because all three where alive the last time I'd been there earlier that day to trade with my contact. (At least I didn't see any bodies) This doesn't sound like the Butcher. Glitch?

Has this happened to anyone else?

Did you capture the REAL killer and not the the mage?

No, that quest messed up. It just won't start. Someone told me it won't because Tova Shatter-Shield killed herself. Another said that it was because I sided with the Empire this time and they now have control of Windhelm. I've heard many more reason as well, but I can't tell who's right because all of that has happened, so I can't pinpoint what the actual cause is. (It worked when I played the first time) Anyway, I've given up on the quest itself. Now, I'm just wondering why people keep getting murdered in the streets. Will this continue until Windhelm is empty of all vulnerable NPCs?

I think it's a glitch where the game thinks the murderer flag to kill an NPC is active but since you haven't reached the appropriate point in the quest as a result of messing up, the game doesn't activate the murder scene yet the NPC still dies as the murder has been activated.

Cant help you man, that quest is considered to be one of the buggest quests in the game, NOT, just buy the house in windhelm and you will be surprised but the quest will start

The steward won't let me buy the house because of a "recent incident" there. (The murderer's hideout) It's a vicious circle. Anyway, I thought the Butcher only targets women?

You can only get the house halfway through the Stormcloak campaign or completing the Imperial Campaign

I've already taken Windhelm for the Empire and the steward still says the same thing. Oh well.
Thank you guys for troubleshooting with me!

That explains it. It's a mad Stormcloak supporter going ape [censored] because you killed Ulfric.

I can't recall the NPC's name, but on my first visit to Whiterun with my last character, I found a corpse next to the well in the market area. I have no idea what happened. My guess is that they spawned incorrectly and took fall damage when they landed.