Sometime in middle or high school maybe, definitely before college, more than 10 years ago, I saw part of a movie on broadcast TV. I missed the beginning but there was a starship that had some kind of mishap in deep space and I think became a derelict. Maybe the later part took place with people in a lifeboat, but it seems more like a derelict now when I think about it. Here's what I remember:

The captain was separated from the rest of the survivors and trapped in an area with rising radiation levels. She (I don't remember the actress, but I remember she was a black woman) had a scene where she was pulling out tufts of her hair, falling out from radiation sickness. The other survivors included a really short man with a cool cybernetic arm; this guy was apparently the main engineer or mechanic and was keeping what few machines were still working to maintain life support. He figured out a way that he could maybe come to the captain's rescue, but it could also kill him so the captain ordered him to stay with the other survivors and leave her to die. She told him they could survive without her, but they would not without him. And soon after she died of the radiation.

They sent out a probe or something to try to call for help, noting bleakly that the universe was ten billion light years across and it was probably pointless.

At one point they saw a supply depot floating in space and were excited...until its slow rotation turned towards them and they saw that it had been hit by space debris and was utterly destroyed.

Eventually the heating systems started to fail, so it started to snow inside. Something about condensation and the air circulation blowing it around.

There was a guy among the survivors who was badly injured. People worked hard to keep him alive, but after the injured man saw another survivor (a man who was pretending to be blind) with secret survival supplies, the faking man snapped his neck, then told the rest of the survivors that he had killed the injured man because he was using too much of their air and they all knew he wasn't going to live. Everyone was upset, but they let it pass because yes, they all knew the man was a goner and their margins for survival for so low. The faker had been secretly hiding away supplies for his own use, and once he had enough that he felt secure he could survive a long time alone, whipped out a gun he had been concealing and started shooting people, starting with the mechanic.

...and then I had to leave to do something, but I never saw the movie again. Haven't been able to figure out what it was, and I want to know the ending because I basically left it at the most cliffhanger-y of moments. And so, good forum folks, if any of you have any idea what this movie was, please tell me. Also what happened at the end?