It turns out that though the twins didn't know of eachother they still did alot of things the same, such as use the same launderette. The twin that was found hanged found out that a photographer colleague had faked pictures of US troops in Iraq and she was going to expose him. He waited for her at the launderette and shot her, only it was the wrong twin that he shot. He then went to the twin who he thought he shot house to get rid of the evidence of his faked photos and she came home, which freaked him out cos he thought he'd just shot her and so he strangled her.