Derek Beck, writing a book about the events of 1775, digs up photos taken of Joseph Warren's skull when his body was being moved in 1855 to Forest Hills Cemetery and uses them to show how Warren was not shot from behind while retreating, but rather facing the enemy front first:
Due to the low muzzle velocity of the musket, as evidenced by their extremely limited range, one can deduce that in order for a ball to pass entirely through the skull, the fatal shot was fired from close range.
Also explained: How Warren's relatives were able to identify his body a year after the British had dumped it in a shared grave in Charlestown by some of Paul Revere's dental work.
Via J.L. Bell.