The friend he spoke about tells his story below.
When a gifted young man believes the lie that there is no ultimate purpose to life, and follows that false philosophy through to it's logical conclusion, awful things can happen. In the video below David explains what did happen because he believed there was no ultimate purpose. It did not have to happen this way, but there is no good reason why it should not have. Fortunately he found the light when his world was at its darkest.
"I will give you a new heart, and a new spirit I will put within you. And I will remove the heart of stone from your flesh and give you a heart of flesh." (Ezekiel 36:26)
He has been accused by many as being Islamophobic. Here's his humorous response.