Endoloution

I think what's missing here is some insight on what the biologist's disposition is to the task at hand.? Is the biologist opposed in any way to killing, but he's being coerced in some way, or convinced that this is necessary?? Is he up for it, but some activists want to stop him?

Something else to consider, is maybe this is just part of the plot.? I think pretty common is where the "policy enforcer" comes across a target that he doesn't want to kill and/or gets targeted himself.? It's a tried and true structure that might work well for this.

Agreed with mikepedley85, unfortunately, dying is unavoidable regardless. Also, is the biologist the main character? If so what's his big motivating event to find a cure for life...?

Do bullets still work? Stabbing? Lethal injection?

In my experience, there has never been a shortage of ways to kill humans other than old age and disease.