The swastika is illegal in Germany and is considered a symbol of hate that evokes the horrors of Nazi Germany and the trauma of the Holocaust.
Police in Germany said on Thursday that they detained a 31-year-old man suspected of painting swastikas with his own blood on dozens of cars, mailboxes and building facades in the central town of Hanau.
Police spokesperson Thomas Leipold said officers were alerted on Wednesday night when a man reported that he noticed the shape of a swastika applied in a red liquid on the hood of a parked car.
Police said that almost 50 cars had been similarly defaced. A test quickly revealed that the substance was human blood.
On Thursday afternoon, police said, the man, a Romanian citizen whose name was not given in line with German privacy rules, was arrested at his home in Hanau, after they were tipped off by a witness.
"He was still under the strong influence of alcohol and his motive appears to be highly personal and job-related — he just snapped," Leipold said.
He added that the man had injuries that appeared to be self-inflicted.
"He is currently being examined at a psychiatric hospital," Leipold said. He declined to provide any further details to protect the suspect's privacy.
The swastika is considered a symbol of hate that evokes the horrors of Nazi Germany and the trauma of the Holocaust.
White supremacists, neo-Nazi groups and vandals have continued to use it after the end of World War II, to stoke fear and hate.
Hanau was in the headlines five years ago when a German attacker shot and killed nine people with immigrant backgrounds in a rampage at a hookah bar in the town, in one of the worst cases of domestic terrorism since World War II.
On Thursday morning, before the suspect was apprehended, the city's Mayor Claus Kaminsky expressed shock.
"Especially in our city, which was deeply affected by the racist attack on Feb. 19, 2020, such an act causes deep consternation," he said, adding that the city had filed a criminal complaint, German news agency dpa reported.
"What happened here crosses every boundary of decency and humanity," Kaminsky said.
"Swastikas have no place in Hanau. We will not allow such symbols to sow fear or division."