My guess is he did love her a lot! but it was the jealous, controlling kind of love. I think the cell phones are key & are going to reveal some Valentines day text message from that Rugby player or some other guy. She must have had plenty of other guys trying their luck, I'm sure... The insecure hot headed guy Oscar was, I think he went through her phone, discovered a message from some guy, lost his cool & confronted her with it, threatened her, chased her with the gun in a state of possesive rage, she fled down the passage and locked herself in the toilet...bang! bang! bang! bang!
A case of...if I'm not going to have you nobody else will!