I believe it was a thriller, but I remember also being slightly scared.

I know it was a while ago since I've seen the film so it isn't that recent of a film.

A SWAT team/ police team/ FBI team /CIA team (I don't remember which). The entire team goes in to investigate a murder. The point of view is told from the point of view of the protagonist, a male, who makes it to the very end, but dies cause the killer is one of his own team members. The female makes it though, but it's all very bloody, and it ends by a pool I think, where she kills the killer. There was a lot of blue lighting, and I think they may have all been stuck on an island or something, waiting for backup.

I keep thinking it was Colin Farrell in it, but I don't think so cause I looked up his movies, and none of them fit... it's not SWAT.

Any ideas on what film this was?