Well it's not exactly a horror game, but it is a police themed adventure game with plenty of murders and stuff. It's my favourite AGS game. And the game I'm talking about is Pleurghburg: Dark Ages. You can get it from
http://www.gaspop.com/ I very much reccomend it, and I think that we should get it on the site here, Alos the graphics may not look that great, but don't let that put you off.