So I have a two dimmer light switches in my apartment, one is connected to a light fixture on the ceiling, the other is an open box on the ceiling that used to house a ceiling fan and or light, I'm not sure. I purchased a fixture and attempted to wire it in, when I looked at the open box on the ceiling, I noticed that there are two incoming cables, one with two wires (black white) and one with three wires (black red white). The cable is BX so the ground is the sheathing. First wired the light black to black and white to white. Turned the power on, and the light worked, but the switch didn't turn it off. So I opened the switch box up, and it seems like the dimmer only has two wires coming in... black and white.
So I'm left a little stumped. My first thought was, why does the one cable had a red wire, my second thought was, perhaps I'm assuming the switch is hooked up to that junction box and I'm wrong. I'm looking for some advice on how I can A determine if the switch is hooked up to that box at all and b figure out how to wire the light so I can turn it off. I'm attaching some photos for reference.

Sorry, if this is an apartment then you have NO place doing any wiring there. PLEASE call the landlord.