The perpetrators apparently belong to the right-wing "Identitäre" (Identitarians) group.
The man did not give any information at first, but in the meantime has agreed to cooperate and confessed to the crime.
Despite early attempts to extinguish the fire, the wooden altar was destroyed and a statue of the Virgin Mary was damaged.
The plaque at the memorial for the victims and resistance fighters from the rank of the ÖCV was smeared with anarchist symbols.
Four people were arrested immediately and the local government initiated a new security strategy for the area.
Reports say the tremors were felt as far away as the Austrian capital, Vienna.
Churches will remain open for individual prayer throughout the day.
On the 2nd of November, a terrorist attack caused the death of four people in Austria.
Police shot dead another suspect who was armed with an assault rifle and was wearing a fake suicide vest.
Yesterday evening, shortly after 8 PM, terror attackers opened fire on passersby in six regions of the city centre of Vienna