So the other day I watched a video on youtube of a BP killing and constricting a fat mouse. The thing that made my stomach turn and question if I could do this is when the BP caught the mouse and constricted it blood came out of the nose and mouth. I was wondering if this is normal? If it is I don't think I can feed live, like I wanted to. Also, is it normal for the mouse/rat to scream when being attacked (stupid question but I need to be sure).

My moms friend had a boa when they were younger and she said she never remembers blood when feeding the snake.