Another great artist gone this month... 🙁
The chart could hardly be more eloquent. Prince is not personally connected to the querent therefore he is L7. Mars is aptly on Antares for someone who just passed away.
What planet has power over Prince and his death? Mars is in Sagittarius so, its dispositor, Jupiter.
Jupiter is his L12 and sits on the 7th cusp by antiscion. The South Node is inside the turned 12th cusp spelling an unfortunate outcome from the matters of that house.
My guess is that the autopsy and investigation will show some house 12 activity to some degree. Not suicide necessarily but excess or abuse of some kind.
What was the last aspect with Mars?
Venus trined Mars and translated its light to Saturn. Venus is in house 7 thus influences the outcome. I will not speculate too much on what Venus could be except that as a natural ruler, in addition to it being on Uranus, it could be associated with the desire to eliminate pain.
We know Prince was ill and can safely assume that he was under medication/treatment. His medication/treatment is Saturn, the ruler of the turned 10th house from the 7th. Pluto afflicts that house cusp and Saturn itself sits on that cusp by antiscion, acting as a flag.
I will not be surprised if the abuse or excess is connected with medication which in turn killed him. Perhaps pain-killers.
Finally, once we know the autopsy results we may come to know whether the Sun and/or Moon have anything to do with his passing. As accidental rulers they are his heart and his lungs respectively. And the Sun being in house 7 has an influence on the outcome.
We will wait and see.
Update (June 3, 2016):
The autopsy report confirmed that Prince died of an accidental, self-administered opioid/pain-killer overdose.