Cruz started firing and within 6 minutes and 20 seconds he had killed 14 students and three teachers. He critically injured at least three other people.
When he stopped shooting he dropped the gun and mingled with the students leaving the building. Outside he bought a soft drink and carried on walking for two miles until he was identified and picked up by the police.
Much of the world at this point said: "Oh, how horrific - but we are not surprised. How long before it happens again?"
The United States loses the equivalent of the population of Whanganui to guns every 15 months or so. The news media in the US can now differentiate between mass killings and "everyday gun violence". The world looked on and expected it all to fade away as it had done so many times before. But it didn't.
The kids at Mary Stoneman Douglas High School realised that their friends and brothers and sisters had been murdered and the government was saying: "Aw shucks, that's life".
President Donald Trump suggested teachers should be carrying guns. I happened to be teaching in Whanganui a day or two later and discussed this with my class. I pointed out that when the gunman came through the door at the back of the class and I was at the front with my gun, they would be between two shooters.
Former presidential candidate Rick Santorum says all students should learn CPR so they are ready when the shooter arrives.
Social media comes alive with older people claiming these kids are too young to know what they are talking about. Government by Twitter elaborates on plans to recruit teachers from the ex-military personnel who are well trained in being calm under fire. This would also be solving the problem of mentally crushed ex-servicemen sleeping on the streets.
So the surviving students realised they were on their own. They organised a march and called it "March For Our Lives", with the date fixed for March 24 (on March 23, a 16-year-old Maryland girl was shot by a jilted 17-year-old boyfriend who then shot himself).
An increasing number of young orators found they had powerful words to say calling for reform of America's gun laws, and that the world was beginning to listen. It was going to be a march in Washington where about 800,000 people turned up but if we add the marches that happened in many cities across the US and in many other countries across the world (including New Zealand) the total will be several million.
More than 50 per cent of the people at the Washington march were over 26 and many were much older. Have the kids hit a raw nerve of conscience in the older generations who have allowed this mess to happen?
And now the silence. The marchers have gone home, many of them back to school.
I checked the online New York Times and Washington Post this week. No mention in either of the "March For Our Lives", but I did find at the bottom of one page a mention of a Chinese exchange student in Florida who had been found to be buying weapons (legally) but who was sent back to China for not attending class which broke the rules of his visa.
But mostly silence ...
We know that teenagers do not read newspapers, so is the apparent silence genuine? Children in primary schools in Whanganui regularly communicate by safe social media links with other kids across the world. I use social media to keep in touch with people I have met over the years in several parts of the world.
I see the news on the ground as it happens. I respect the editor of our very own Chronicle as a man of integrity with respect for getting at the truth, but increasingly in the US, news seems to have little to do with reality.
It is said that without Facebook, the Arab Spring would not have happened. The millions of people that took to the streets on March 24 were not brought together by the usual news mediums. It was Facebook and Twitter and the many other channels of instant electronic communication that got the march going.
There may be quiet now but, believe me, they are talking.
The real effects of this movement, which is not simply about guns but about violence in the world, will be seen in the next few years when these youth begin to vote.
Frank Gibson is a semi-retired teacher of mathematics and physics who has lived in the Whanganui region since 1989.
