Every Muslim is an empowered vigilante commanded by the Koran to wage violent jihad against “infidels” whom they think have insulted either Islam, Mohammed, or the Koran.
As in, “Kill the infidels wherever you find them!” - Sura 9, verse 5.
Every mosque is an enemy fortress and must be treated as such.
And Geert Wilders was there. High profile target if they had gotten him.