In Hong Kong we dial 999 in an emergency. In the US the number is 911. In fact 911 can also be used in many other places. Tomorrow we remember that 9/11/2001 was callously chosen as the date for terrorist attacks on the US in which around 3,000 people died.
The attacks were masterminded by Osama Bin Laden and his al-Qaeda group. People with links to the same group had carried out a previous attack on New York's World Trade Centre Twin Towers - in 1993, when a truck bomb killed 6 people and injured more than a thousand others.
Why the Twin Towers? Why not some other target? In 2004 Bin Ladin said the idea of destroying the towers first occurred to him in 1982 when he witnessed Israel's bombardment of high-rise apartment buildings during the Israeli attack on Lebanon which killed thousands of civilians.
In the minds of many people, perceived US support for injustice by Israel to other peoples in the Middle East was, and is, a major cause of terrorism in the world. Such support and such injustice must be dealt with to remove the conditions that breed terrorism.