Terrifying is the proper term. The only time I've ever been
really mad with a co-worker is when they decided to do a demo to potential customers with the newest (pre-release) firmware of a massive lathe without my very explicit permission. That could have well ended up with people seriously injured, as it was - of course - it happened to have a pretty bad bug in it but besides people getting scared it didn't cause any damage or injury.
My own process to ensure things were safe was to first run it in air without the spindle powered up, then on foam, chalk, and finally on aluminum in that order before progressing to steel.
And that saved my ass more than once.