I strongly recommend you read the book Amerithrax [0]. The book gives some historical examples of malicious groups [1][2] trying to use biological agents. Also, it is far harder to weaponize biological weapons than people think.

Notes:

0 - https://www.amazon.com/Amerithrax-Anthrax-Killer-Robert-Gray... . Amerithrax was the name of the FBI investigation. https://www.fbi.gov/history/cases-and-criminals/amerithrax-o...

1 - https://en.wikipedia.org/wiki/1984_Rajneeshee_bioterror_atta...

> In 1984, 751 people suffered food poisoning in The Dalles, Oregon, United States, due to the deliberate contamination of salad bars at ten local restaurants with Salmonella. A group of prominent followers of Rajneesh (also known as Osho) led by Ma Anand Sheela had hoped to incapacitate the voting population of the city so that their own candidates would win the 1984 Wasco County elections.[2] The incident was the first and largest bioterrorist attack in U.S. history.

Tried to take over a town by making all the voters too sick to vote on election day. This event is why all buffets & salad bars in the US now have sneeze shields.

2 - https://en.wikipedia.org/wiki/Aum_Shinrikyo_and_weapons_of_m...

> Aum Shinrikyo operated the most extensive biological weapons program by a non-state actor ever discovered. Aum considered a range of agents, but only seriously attempted to obtain and disperse Bacillus anthracis and botulinum toxin, the causative agents of anthrax and botulism. With the 2001 anthrax attacks, it comprises the only attempts to use anthrax as a weapon not attributed to a state program.

Tried multiple times to weaponize anthrax and failed. This was a group that made an automated factory to build AK-47s. Eventually, they spread sarin nerve agent in the Tokyo subway.