Japan's Kaguya lunar orbiter

On June 10 the Japanese probe named the Kaguya lunar orbiter was purposefully crash landed on the moon's surface.

http://www.newscientist.com/article/dn17271-japanese-probe-set-to-crash-into-moon.html

The Anglo-Australian Telescope captured images showing a bright flash at the time of impact.

My question is:
What was the bright flash composed of?

Was it simply a could of moon dust thrown up upon impact and if so why was it just a brief flash instead of lingering for a few moments.

or

Was the bright flash the result of the 3 ton probe impacting the surface at 4,000 to 6,000 mph and generating heat and light as the forward momentum was converted to friction and energy.