Well, how about this: there is a lot of knowledge that if it were publicly available in a useful form, could do incredible amounts of damage. From viral DNA/RNA

Well, how about this: there is a lot of knowledge that if it were publicly available in a useful form, could do incredible amounts of damage. From viral DNA/RNA sequences to the exact procedure to get a fission cascade. The exact chemical formula to a lot of different nasty concoctions, or in some cases just the fact that particular things even exist (e.g. you don't need radioactive material to create radiation poisoning ... even mass radiation poisoning) Advanced knowledge has only once been used in a terror attack, and not very effectively. These types of drone would need to collect a lot of not-so-easy-to-get knowledge. You'd need weapons, mechanical design, electronic fuses ... but mostly an AI good enough to make decisions on their own. And frankly, with good AI you could do a lot more damage than this without ever killing anyone.