I am so sorry for your loss. I know this may sound completely cliche, but things do get better with time. Now is not the time to make any decisions.... and I'm sure it's not just medicine that seems irrelevent...just "give it time" and TALK TO SOMEONE (no, computer posting boards are not sufficient).
A year and a half ago one of my students...a sweet, kind, 16 year old honor student, was shot to death on her front steps as she came home from (no joke) bible study. He mother could do nothing but hold her as she bled to death. So far, no arrests. No clues. I taught at a very small school, so it was obviously devastating to our community. HOwever, as I look at the incident from the perspective of 17 months, it has had a profoundly positive effect on my life, as well as the lives of many of my former students. I no longer take anything for granted. Specifically, my family always knows how much I love them, and I feel more confident than ever that teaching is what I was meant to do with my life...believe me, I almost quit a thousand times in those few days after Becky's murder. Use this incident to reevaluate your life, and what you want to accomplish. If medicine was so important to you before this incident, I feel that it will be just as important, if not more, once you have made it through this rocky time.
Best Luck.