“Sales engineer” sounds like one of those positions that would be regularly setting up demos for customers and have access to the equipment and basic operating procedures.
“Could we use this to burn paint off the road” sounds exactly like the sort of question a person doing a demo might say “I don’t see why not, let’s try it” to.
While with deliberate thought about it, the fact that road markings are retro-reflective is obvious, but it’s not something you would necessarily consider immediately, since it’s called “paint” and almost all paint you encounter in the world is not retro-reflective.
For the rest of it, my reading of the story is multiple things happened here:
1) They initially aimed the IR laser at the paint on the ground. The paint being retro-reflective the laser damaged itself in about an half hour and stopped producing consistent results, just occasional spots of results.
2) The sales person rather than halting the demo to get someone else to take a look at what was malfunctioning continued to fire the laser after making various adjustments not realizing that because the laser had been damaged it was firing not at the ground anymore, but at the car a few spaces away.
3) They’d been messing with the laser after malfunctioning since before the VP parked their car, so there’s possibility they were sending lasers in the direction of the other building, so that’s one issue which would have been bad enough on its own but…
4) At some point the VP parked their car in the path between the laser and the building. As they continued to mess with the malfunctioning laser, they burned through the paint on the side of the car, exposing the bare metal underneath.
5) The bare metal is also highly reflective, but because it’s not retro-reflective the problem is now you had completely uncontrolled reflections. The ones that went backwards had nothing to stop them since there was only a fence and field between the lot and the school. And the ones that went up obviously also had nothing to stop them since they were outside.
6) Because of the unknown detections and quantity of reflection, in addition to getting all the potentially exposed employees and customers checked out, the company would also have to make advisory calls (at a minimum) to the school and the local airports and military installations.
Whether those schools and planes were actually in danger or not could not be said with certainty, but the point was less “oh know we’re terrorists now” and more “this was a huge screw up, and I need to impress on you why it was bigger than just breaking company property or not wearing your safety gear”