German police confirmed some arrests in Berlin on Sunday.
The picture painted by police showed the suspect as a Muenster resident who was apparently financially well off but was frequently at odds with authorities and in court often.
German police have detained four men, one of whom they suspect of planning knife attacks at today's Berlin half-marathon, the newspaper Die Welt reported in its online edition.
The prosecutor's statement said no one was detained during the raids.
"The crime scene investigators are checking out the crime scene, trying to identify, investigate and secure traces". They asked the public to only trust information provided by authorities. The man was believed to be a German citizen, he said. Germany has very strict privacy laws on medical issues.
Authorities said a motive remains unclear.
"So far, we have not found any evidence of political motivation behind this attack", chief prosecutor Elke Adomeit told reporters on Sunday. "But he was well known to the police".
A source close to the investigation said that incidents related to the perpetrator's mental health had affected his family since 2015, and that he said late last month that he wanted to commit suicide.
The prosecutor said Jens B. had run-ins with the law relating to violent conduct, property damage and fraud, but all charges had been dismissed.
The two people killed were a 51-year-old woman and a 65-year-old man, both from northern Germany. Their names weren't given, as is customary in Germany.
Early on Sunday, all three bodies were taken from the crash scene in front of the well-known Kiepenkerl pub.
Reul said two people were killed in the crash and the driver killed himself - lower than the earlier police toll of three dead plus the driver.
A search of the man's Muenster apartment late Saturday turned up more fireworks and a deactivated AK47 assault rifle. Police also found several gas bottles and canisters containing gasoline and bio-ethanol, but did not know yet why they were stored there.
An unknown number of Dutch nationals were also injured in the melee, officials said.
Armed Police officers are seen at the scene when several people were killed and injured when a auto ploughed into pedestrians in Muenster, western Germany on April 7, 2018.