why girls were killed?

Spoilers obviously

For money and because they obviously liked doing it. But there were 3 of them involved in it, Alfonso (the factory owner) was the guy who had sex with Marina the day before (after Quini had tied her up to the bed). He was the photographer of the torture porn shots but he also got away with it because he was only identified by his watch so the evidence was sketchy and he bought his silence by giving in to his workers demands and started paying them a decent wage.

*SPOILERS*










My take was that there were two separate things going on:

One, Quini was pimping the girls to Corrales for the rich old man's sick enjoyment. He used photos of them to keep them quiet. Remember, he bought film every month, so this must have been an ongoing arrangement. Corrales probably paid him to locate girls and bring them to him. The other person in the photo was Corrales - you could tell by the watch - but he was a powerful man locally and the cops did not have enough proof.

Two, Sebastian was a pedo who just happened to be hiding out at the lodge. He saw the girls when Quini and Corrales brought them to the lodge and figured they would make easy victims for him. He probably befriended the girls and offered them a way out of town - the hotel jobs- so they could be free of Quini and Corrales. Remember, the mother of one of the dead girls said Sebastian was helping her daughter "get over" Quini.

Once Sebastian had the girls convinced to leave town with him, he would imprison them in that room at the lodge, rape and torture them and eventually kill them. He probably started killing them because he'd left his previous molestation victims alive and ended up in trouble with the law. Killing them would keep that from happening.

Anyway, that's how I saw it.

The movie was a bit too vague about the identity of the killer and his motivations. The only thing that was clear to me from the movie was that Quini was the pretty boy who lured girls into the ranch for somebody to have sex with them and kill them. But who was this somebody? I could guess it was probably the rich man, whose hand the policeman shook during the strike. But this man was only shown once during the movie and, to my knowledge, it wasn't stated very clearly that he was the killer. Also, the caretaker of the ranch, who was stabbed to death at the end, was only shown for brief moments and I didn't quite get it what was his part in the whole thing.