You know, they're not discussing the cause of death. Unless I've missed something, it's just not mentioned at all. This article mentions "causes of death unknown" -
http://news.bbc.co.uk/1/hi/england/suffolk/6164475.stm This suggests a lack of violence. And they're not sexually assaulted. And the clothes are missing. So what nutter strangles women, keeps their clothes and puts them in water. I'd be slightly easier about it if he were sexually assaulting them - would make a lot more sense. Scary times.