Even after 30 years, the facts of the Dunblane massacre are hard to comprehend.
On the morning of Wednesday 13 March 1996, a gunman entered the gymnasium of the town's primary school and, over the course of less than four minutes, murdered 16 children and their teacher.
Another 12 children and three adults were either shot or injured in the assault. All but two of the children attacked that day were aged just five and six.
The horror of the murders was matched by disbelief. How could this have happened in the UK? How could it happen in such a small, quiet place?
And how had a man been able to walk into a school armed with four handguns and more than 700 rounds of ammunition to commit mass murder?
