Sandy could be the cause for the death, Ranvijay might have had an hit and run and Sandy's blood group will not by B as requested by the nurse. See an article about blood donation here
If you have blood group A then you've got A antigens covering your red cells.
Blood group B means you have B antigens, while group O has neither, and group AB has some of both.
The ABO system also contains lots of little antibodies in the plasma, antibodies being the body's natural defence against foreign antigens.
So blood group A has anti-B in their plasma, blood group B has anti-A (you probably get the picture at this stage).
To complicate matters though, group AB has none and group O has both of the antibodies.
Which means giving someone blood from the wrong ABO group could be fatal.
The anti-A antibodies in group B attack group A cells and vice versa.
Which is why group A blood must never be given to a group B person.
Group O negative is a different story.