Sounds like a truckload of primers ignited, incredibly tragic

https://fox2now.com/news/illinois/fatal-explosion-at-olin-corporation-in-east-alton-illinois/amp/

Wow that's sad for the driver having died as a result.  Not sure what started the ignition of the load of primers or primer materials.
We all know and understand the sensitivity of the primer mixture.  However in large quantity it can be very explosive and heat, flame, shock or spark sensitive depending on the status of the mixture.

When the make primer mixtures the formula is usual wet o reduce the possibility of dentation during primer manufacture.  Then they are dried out for the final product to be packaged.

Thanks Wade, Vista Outdoor (about 40 minutes away) the owners of Federal Cartridge, Speer, as well as others is a huge place. They must have some serious safety protocols in place to never have these issues, at least not on this scale

Reports are saying it was a semi-truck load of shotshell primers.  That creates more questions than answers for me.  Finished shotshell primers ought to be pretty stable, and usually are packaged to prevent chain detonation.

Absolutely have safety as a very high priority when it comes to handling products as such.  Buildings are likely separated / spaced just incase something does go wrong to lessen the damages.
I wish I could learn more of what went wrong with the Winchester explosion incident.  One thing that comes to mind is possible deliberate suicide...so many possibilities.

For sure, at the Vista Outdoor plant / old federal cartridge factory, everything is separated as you mentioned.

I'd guess some sort of fire before explosion.  Heat gets to the flash point of the primer mixture and the reaction just happens. 

Greg

So many igniting at one time is what makes it so odd

I was just at my local shop and bought 2000 small pistol primers that are Winchester. I have used them for 50 years.  Craig

Yep, they have worked well for me also. I tend to favor CCI for some reason, but Win primers do just fine

My Bosnia primers worked fine but I am down to 1500 or so. The local shop has all primers but nothing cheap all in the 100/1000 range.  Craig

I?d even be ok with $70.00 / 1000, double what I used to pay, but $100.00 / 1000, that?s still hard to stomach

Ken I have seen all kinds of pricing from American. You pay less for a more slightly damaged bullet but I have seen double the quantity for half the price for no real reason. I would think it's cost and or quantity on hand etc.   Craig