Do you think it would take less than 9 hours to pour some diesel fuel on fertilizer and flatten the entire WalMart?
People will just move on to other weapons: knives, bombs, etc.
Norway has very restrictive gun laws. Breivik managed to get enough fertilizer to make a bomb that was mostly a distraction, but still sent 8 people to grave and injured hundreds.
UK is having a knife problem: https://www.bbc.com/news/uk-42749089 https://www.bbc.com/news/uk-48186035
You are at 10x higher chance of death by vehicle.
The -only- reason it is seen as a tragedy because people feel those deaths were somehow avoidable.