According to the indictment, the man had two primed sharp hand grenades with the intention of using them against other people at the time.
The man, according to the indictment, threw an unsecured hand grenade at a location where several people were present, but it did not detonate. The man then tried to flee but was caught by people in the area.
"This evening was a warm and fine late summer evening, and many people were therefore outdoors in the yard, both adults and children. What then happens is reminiscent of pure war actions", says prosecutor Adrien Combier-Hogg in a press release.
He notes that the incident could have had "completely devastating consequences" for the victims and others in the area.
The investigation has shown that the 18-year-old had no relation to the victims, and he is believed to have taken on the assignment for payment.
The evidence consists, among other things, of a large number of interrogations, chat conversations, and video recordings from surveillance cameras.
He is now being prosecuted for nine cases of attempted murder, attempted gross endangerment, and gross violation of the law on flammable and explosive goods.