First you must decide whether it is worth your time to investigate. If you are busy and have a very important job, if you are responsible for a million dollar project, you might not want to waste many hours and headache on this matter. Your boss may see that as a minor task and demote you.
If you decide you may want to investigate, take a picture with your mobile phone of him placing things in his car, subtly. Nr 1 is always = Secure evidence!! Pictures, sound tape recording, anything that holds up in court.
Then of course you can ask him, but with a smile, and keep your mobile sound recording app on. It may be that he has the best intentions in the world, maybe he has got a good deal and bought it. Then take it from there. If he gets mad and tell you to mind your own business, let him know that you will be notifying the boss. Don't let him know that you have taken pictures, otherwise it might escalate and he may attack you.
This post was edited by Taurean on Jan 12 2017 06:24am