There was also an RPG attack on the British Ambassador this summer (but I don’t know the precise date).
Can’t say there weren’t warning signs - only that they were ignored.
Check Canadian travel reports and warnings.
A British Embassy convoy was hit by a grenade on June 11, 2012, injuring one person. An IED exploded at the gate of the U.S. Consulate on June 6, 2012. On May 22, 2012 a grenade attack targeted the International Red Cross offices and an explosion hit a column of UN vehicles on 10 April, 2012. These events highlight that the situation continues to be unstable and problematic.
http://www.voyage.gc.ca/countries_pays/report_rapport-eng.asp?id=162000
Also interesting that on Sept 6th Canada closes embassy in Iran, gives Iranian diplomats in Canada 5 days to leave. I think I will be checking Canadian travel advisories over US.