The two trillion they refer to is Market CAP of public traded companies, thus they litterally say it devalued the stockmarket for two trillion.

Anyways, there was a lot of leveraged speculation involved and / or institutional investors, i strongly doubt the average joe sat awake at night (in europe) and just waited to press sell (and everbody in the same 5 minutes).

Joking by side - my indicators drew the picture that in majority only stocks included in indices where sold off. 

In the end it appears that leveraged speculation wiped of a large part of that stack (to speak in that language), even "solid" names dropped on EU open up to minus 20% (villeroy & boch ag for example, just to climb back to minus 2% (FLASH CRASH INDEED) ) -- it also appeared that leveraged speculators sold pound vs gold once it was clear that leave wins the vote..