An injury to the back of the head causing a nosebleed?

I read this today in Jason Cole’s regular article:

“Likewise, there was a telling moment when former New York Jets running back Curtis Martin(notes) once was tackled so hard, falling backward and hitting the back of his helmet on the turf so violently that he came to the sideline with blood dripping from his nose. Former Jets backup quarterback Ray Lucas looked at Martin and was frightened for him.”

My questions:

  1. How bad of a brain/skull injury would cause the nose to bleed?
  2. Is it more likely that the bleeding was caused by a sinus abrasion or tear unrelated to a brain trauma?

I’m asking because over at Polite Dissent, they often comment on how severe a brain injury must be to cause a nosebleed.