He knew or should have known the potential consequences of the code he was writing. Maybe this could have been you, but it definitely wouldn't have been me, because I would not have committed the first line of code until I was reasonably sure that a) I was not going to kill somebody accidentally, and b) the project had sufficient safeguards.

I'd also like you to note that you're pointing out the lack of accountability as a problem, and then dismissing one of the fundamental mechanisms of accountability: naming people who harm others.

Yes, other people on the project also should have pushed for traceability and accountability. But responsibility is not zero sum. "I was just following orders" is never an excuse for killing people.