Not much is known about Bernhard Graumann, a 59-year-old German gardener who died Friday in his home in Mehlingen, Germany. But reports indicate he enjoyed making things blow up, and authorities are now warning people who might have had bad relations with him to be extremely cautious.

Those who knew Graumann say he was a performer and made the most of his explosives license — utilizing pyrotechnics to add an entertaining flair while reenacting scenes from the Middle Ages. He also dabbled in re-creating antique firearms that use gunpowder, according to the BBC.

But local authorities fear the man also used his expertise for significantly darker purposes, to rig booby traps prior his death intended to harm his enemies from beyond the grave. The Associated Press reports one person has already been killed and two others were harmed in recent days because of hidden bombs. Police have linked those bombs to Graumann.

“It cannot be ruled out that the deceased made other preparations that could endanger further people,” local police said, according to the AP. Authorities say more than 60 people have called a hotline set up Monday — primarily from former associates of Graumann fearing they could be next.

On the day of Graumann’s death, a 64-year-old doctor in a nearby town was killed in an explosion.

The physician’s death was no accident, German police told the BBC — the doctor succumbed to a disguised explosive placed outside a medical practice, programmed to detonate when removed from the ground. The sinister case took another turn Sunday morning, when a 37-year-old woman and her 4-year-old daughter were injured by shards of glass after placing a log rigged with explosives into a wood-burning stove.

The woman and her daughter are expected to survive, but police say someone placed the booby-trapped log inside their home, according to the AP. Graumann is identified as a suspect in both incidents, and on Wednesday, bomb-disposal experts removed another rigged log from the home of a different woman, who apparently also had issues with the gardener.

“He had a personal or business connection with the victims,” German police said in a statement to the BBC, adding that there had been “conflicts in the past.” They have not ruled out the possibility that Graumann hid more traps before he died.

Police say there are no signs of foul play in Graumann’s death, although an autopsy report is not expected until next week. The AP notes it is unusual that his full name was released, but authorities identified the man to warn others who knew him. They’ve since discovered gunpowder and other items associated with explosives inside Graumann’s home.

“People who have had a problematic private or business relationship with Graumann are urged to contact the police immediately,” German police told the BBC.

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