As I said, I don't care for off body carry. But if the work case goes from his Home office, to his office and is secured at those locations (even if just behind a locked door) then it is not in fact irresponsible. It is not an uncommon form of carry for those who do have to go through the security to get into courts. They are known to the Courthouse security forces, and the bag is expected to have the firearm in it, while letting the individual quickly go through the magnetometer without setting it off as the security team sees the well known bag and it's expected and authorized firearm.
Yes he made a mistake, but not a criminal or really irresponsible one. There was no intent, and it really was a last second, have to grab another bag issue. I do prefer on body carry, but this kind of carry is not irresponsible or wrong. Contrary to popular belief, if you train your kids a firearm does not have to live in a safe anytime it is not on your body. Many of us grew up knowing what firearms were and that they were not to be touched and they could in fact be safely left unlocked.