They do at the end 1. it allows the assassins do get away since there is a delay compared to a gun 2. it's formally deniable 3. it's informally obvious who did

They do at the end 1. it allows the assassins do get away since there is a delay compared to a gun 2. it's formally deniable 3. it's informally obvious who did it 4. the people in charge of doing the killings are also in charge of the development of it, so it might have been easy for them to get access