How does Ali become an orphan?

Ali's parents were killed by a car, which was driven by a man who was high on hasish and wine.

From the text:

In 1933, the year Baba was born and the year Zahir Shah began his forty-year reign of Afghanistan, two brothers, young men from a wealthy and reputable family in Kabul, got behind the wheel of their father's Ford roadster. High on hashish and _mast_ on French wine, they struck and killed a Hazara husband and wife on the road to Paghman.