Rhineland-Palatinate Police said in a news release that gardener Bernhard Graumann, 59, was found dead in his bed in Mehlinhen, near Kaiserslautern in west Germany, on Friday night.
Earlier that day, a 64-year-old doctor in a nearby town was found dead in front of his practice after an explosion. Police believe the bomb may have been in a package that was left in front of the office as part of a "booby trap" which the doctor picked up, triggering the blast.
Two days later, an "explosive-engineered log" exploded in a wood-burning stove at a home about five miles from where Graumann lived, according to police. A woman and her 4-year-old daughter were injured in that blast.
Police said all three had been known to Graumann, who either had a "personal or business" connection to the victims.
"Graumann did not have a good relationship with these people," police said, adding that there were prior conflicts in the past.
"The police cannot rule out the possibility that the deceased made preparations to endanger the lives of other people before he died," officials said. "In particular, people who have had a problematic private or business relationship with Graumann are urged to contact the police immediately."
Investigators are also probing whether the 59-year-old poisoned himself, with autopsy results expected by next week, Sky News reported. Investigators searching his house discovered gunpowder and weapons.
Graumann was active in a medieval club and had often dealt with black powder, local radio station SWR reported. The 59-year-old was "very withdrawn," but was married with two children, according to the radio station.
People who knew Graumann said he was involved in Medieval reenactments and had apparently used pyrotechnics as part of the entertainment.
"He always went to medieval festivals, had a knight's armor," acquaintance Siegfried Zech told RTL television. "He's also said to have had an explosives license and have handled a lot with explosives and weapons, but supposedly he purchased all of that legally."
He also had had a history of incidents with the police. SWR reported that in the 1980s he tried to shoot the ex-boyfriend of his girlfriend at the time.
Westpfalz police spokesman Bernhard Christian Erfort told the Associated Press on Wednesday they'd received more than 60 calls to a hotline since it was established Monday, but no more bombs were found.
A third loud bang was heard around lunchtime on Thursday, prompting a flood of calls to a police hotline but it remains unclear where it's linked to the other attacks, The Times of London reported.
The Associated Press contributed to this report.