I am familiar with the photos that you are referring to.
I now believe that Krystle's legs were still attached, but underneath her in the most graphic photo. Her left leg is bent up backwards underneath her. The sole left shoe is visible and is a Chucks style shoe sole. The leg is bent at the knee and her right shoe, showing a bit of teal, is visible just above where the denim is spread on her left leg. In the more clear photo, with the paramedic checking her pulse, you can see her right leg bent in the same angle. I believe that she was transported in an attempt to save her. I believe that she was still alive in those graphic photos.
ETA: Image link on stretcher...
http://onpoint.wbur.org/files/2013/04/0416_marathon-trio.jpg
I do not have links to the graphic images, as they are no longer online, I don't believe.
The other photo of the older man in the wheelchair in the navy sweatshirt...there are more photos of him circulating, one of which is him lying on the ground. His sweatshirt is pulled up, so it is harder to see, and a man with camo is standing to the left in the photo with a man in tan pants standing to his right.
http://ww3.hdnux.com/photos/21/04/60/4475918/3/960x595.jpg