I saw this movie 2 years back and now I don't remember the name. I tried searching it on Youtube also but due to lack of information that I have I am unable to find it.
It was a Hollywood movie in which a group of people (for training) was sent to a lonely island. Then each person was murdered one by one but nobody was able to identify who the murderer was. At the end the murderer was one of the persons in the group.