On Wed, 17 Jan 2018 09:56:58 -0800 (PST)
Simon Jester wrote:

So the brakes, or lack thereof, were not relevant.

He sprinted to get past the truck then was suddenly thrown off the
bike. If you forget you're riding fixed-wheel there's a tendency for
the bike to launch you when you try to leave a leg extended, as you
might to prevent pedal strike when swerving. The fact that the bike
had no front brake probably wasn't relevant but it being a fixie may
have been the cause of the crash.