This is a long-lived, active species so that behavior only seems to be explainable by a recent outdoor pesticide treatment. If you found them all around one gas station it makes sense; over a wide area not as probable even though they do fly and wouldn't die immediately.
For clarity:
At 8:00 PM my family was shopping at a large strip mall with a lot of parking and parking lights.
We found two beetles. (They gave off the stink defense as we bagged them in a shopping plastic sack.) We could have collected many more.
Drove 6 miles to a grocery and my son and I waited in the car as my wife ran into the store. Outside the car many of these beetles could be seen on the ground. We got out of the car and got the bag and collected 4 more. We could have kept collecting but the sack was stinking and they where frantic all over each other.
Brought them home and put them into a critter keeper. All beetles were very active and had full use of all limbs. Not so much more smell.
Next morning. All collected beetles were on their backs and their back legs had become dormant(?) extended and usless for keeping themselves upright. Turned a few over and they would crawl about and the useless back legs cause them to tumble upside down!!
On the way to church saw many of the beetles outside upsidedown with the same leg condition.
Collected beetles are not dead but they are all upside down.
I am not real familiar with beetles and their behavior but this seemed to be a spike in activity in our area. I had not seen this many of these before.
I read more on the linked bug net pages how these beetles can hibernate overwinter.
I have six still.
