I did not intend my comment to be rude and I am sorry you felt that it was :-(
I think you'll find that in many jurisdictions a general duty of care also extends to individuals. If A is employed by a security firm and carries a firearm when on the job, and he decides to show it off to a group of schoolkids taunting him, and he shoots one or two of them, then his employer may well have failed in its duty of care, but are you really suggesting that he walks off scot-free on the basis that he was in employment at the time of the incident? I doubt very much that he could. In many or most states, he would likely be prosecuted, and prosecutors would likely try to establish negligence (assuming no one believes the shooting was deliberate). Negligence is intimately bound with the concept of duty of care, for negligence is breach of that duty.
The problem with this example is two-fold.
First, the case at hand with the Concorde is most definitely not this case. Playing with a loaded gun is a far cry from playing with a scrap of metal on an airplane.
Second, your example would fall under the second exemption that I noted, which is actions which are otherwise innately criminal. In the USA unlawful killing has many forms and in this case he would most likely be charged with manslaughter, which is a criminal change.