Don't know if this will help but...
I had essentially the same symptoms: huge bruise on my upper arm, front and back, and could not lift it to 90 degrees. There was even a little sack of blood just above the elbow.
For me it was a torn pec, which is healing and re-habbing now.
I strongly recommend your friend see an orthopedic immediately. I was told that if mine had been a major tear that is required attention sooner than a week.
I was confused since the pain and bruising was not in the pec area. You just never know. That's why its best to see a doc.
BTW, now, a month later, the blood has drained into my forearm.