Tim K went on the rampage in his former secondary school on Wednesday morning, killing three teachers and nine students between the age of 15 and 16. The 17-year-old shot dead three more people in a supermarket car park as he tried to flee armed police officers, before later turning the gun on himself.
Flowers and memorial candles have been left outside the Albertville school, while mourners at the church service lit candles in memory of the victims.
Flags were flying at half mast on Thursday at the order of Interior Minister Wolfgang Schaeuble.
The head of the Evangelical Church in Germany (EKD), Bishop Wolfgang Huber, said the families of the victims and the perpetrator were in his thoughts and prayers, according to the Evangelicalische Pressedienst.
The Evangelical Bishop of Wuerttemberg, Frank Otfried July, said: “As a father myself, I stand stunned before this event.”German Chancellor Angella Merkel said it was a “day of mourning for the whole of Germany”.
"Our thoughts go out to the families and the friends. We are thinking of you and we are praying for you,” she said.
A spokesman for the EKD told the Evangelicalische Pressedienst that more than 15 spiritual counsellors had arrived in the town to offer support to survivors and local residents, while many more priests were standing by ready to help.
