At some point in time, someone attempted to grow explosive fruit. Perhaps they imagined an orchard of grenades, tuber minefield, or simply a cheap source of explosives. The remnants of the project, and its greatest apparent success are the boomfruit.
Boomfruit are not very dangerous, and takes real creativity to kill someone with one. They are essentially large tomatoes designed to produce nitroglycerin in addition to its normal juices. A typical boomfruit contains just enough to pop dramatically on any hard impact. They are popular at protests, concerts, and public appearances, but most security will have been specifically trained to look out for them.