The three recent mass shootings in the UK were all in rural areas:
Hungerford 1987 16 killed by Michael Ryan
Dunblane 1996 17 killed by Thomas Hamilton
Cumbria 2010 12 killed by Derek Bird
It is clear from these figures that attacking in a rural area gives the murderers more time to kill during their spree. Hopefully any potential terrorists won't have embarked on this particular analysis.