Those who chose not to learn from history are doomed to repeat it.

https://www.theguardian.com/us-news/2017/oct/02/las-vegas-shooting-university-of-texas-tower

In 1966, there were relatively few assault weapons on the market that were convertible to full automatic, and far less awareness of how to do so. Now the instructions for converting a weapon are freely available on the internet, along with kits costing just a few hundred dollars that either help with the modifications or essentially act as crude conversion mechanisms in and of themselves.
There weren't as many AK-47s around in 1966 as there are now, and only a few AR-15s that could be converted, because it was a relatively new weapon...