Ben saves Locke from suicide, then chokes him with the cord

John Locke has returned to the Westerfield Hotel where he has been staying. We see him in a dank room writing his suicide note to Jack. He then throws the phone Charles Widmore gave him in the trash. He looks and the hole in the ceiling and grabs a crutch so he can stand. He pulls the desk over below the hole and pulls an extension cord from a bag with the logo Angels Hardware. He ties one end to the radiator and throws the other end over a pipe in the ceiling, cuts it and ties it into a noose. He slowly pulls the noose around his neck and steps to the edge of the desk. At that moment, there is a knock on the door and it's Ben. Locke looks startled when he hears Ben's voice and before he can do anything, Ben has broken through the door.

Locke asks Ben how he found him and Ben tells him that he has someone watching Sayid and all of them, who he claims he is protecting. Locke suddenly realizes that it was Ben who shot Matthew Abbadon in the cemetery. Locke tells Ben that Charles Widmore saved him and Ben's rebuts that saying that Widmore was just using him to get back to the island. Ben tells him that he can't commit suicide because he is incredibly important. Locke begins to cry a little and says "There is no helping me. I'm a failure." Locke then says that he couldn't convince any of his "friends" to come back to the island and Ben interrupts saying that Jack booked a flight from Los Angeles to Sydney tonight with a return flight the next morning. Ben tells him that whatever he said to Jack worked and that he can convince the rest of them too. Ben drops to his knees telling telling Locke that he has to get back to the island because he has a lot of work to do. Ben then unties the cord from the radiator and helps Locke down from the desk. Once Locke gets down he is weeping profusely. Ben tells them that they should talk to Sun first but Locke tells Ben that he promised not to bring her back and about Jin still being alive. With that bit of information, Ben seems to have quickly formulated a plan in his head. Locke removes the noose from his neck and thanks Ben for his help. Ben says that they can figure something out once they get the entire group together and that's when Locke spills the beans. He tells Ben that they will need to find Eloise Hawking and she can help them get back to the island. Once Ben has this information and confirms that he knows Eloise, he puts the cord around Locke's neck, pulls him to the floor and strangles him. It's hard to tell, but it seems that Ben is actually saddened by killing Locke as opposed to being his usual cold, callous self.

This was probably the darkest scene of the show thus far. It was also probably the most brilliantly acted scene of the show. I just wanted to get that in there.

So why did Ben kill Locke? The possible reasons are many. Did Ben really not know that Eloise was the one who could help them get back to the island? Does these firmly establish Ben as they bad guy in the Ben Linus vs. Charles Widmore feud? I'm guessing it's still going to remain unclear who is bad and who is good or if either are truly good or bad.