Hey there!
To start off with this, we need to know what does the word "biocide" even means.
The term biocide indicates "a destruction of life". There is actually a real bottle of this biocide, it is actually poison that inter's that body and harms and also kills the body.
So, in this case, this is why is is to be considered a destruction of life.
No, we want to understand, when and where would a author want to use this term.
One way that he could use this is by perhaps in the climax of a story, by the author doing this, this makes the reader's very hyped about the story ans there really going to want to find out what is going to happen next.
Hope this helps.