Families and friends of a 17-year-old Islamic State member killed fighting in Syria held a Christian-Muslim service for him in Hamburg's St Pauli Church on Friday.
A photo of the young man, identified only as Florent, was placed next to the altar.
After converting to Islam at the age of 15, Florent changed his name to Bilal and joined the ultra-conservative Sunni Muslim Salafist scene.
"The terror has come close to us with the news of his death," said Lutheran Pastor Sieghard Wilm.
Together with Imam Abu Ahmed Jakobi, Wilm said he wanted to show "that violence should have nothing to do with religion."
However, everything from staging a service for a Muslim in a Christian church to honouring someone who fought for a terrorist organization has raised questions.
"I have had to face a lot of criticism, asking how a pastor can celebrate a funeral for a terrorist," Wilm told dpa in an interview ahead of the service. But he said he has also received support.
"We're not backing away from this tough situation," said the pastor, who knew Florent for years, partially thanks to Wilm's work at a youth centre.
Florent, who grew up in Hamburg, travelled to Syria in 2015 to join the extremist network's efforts to create an Islamic caliphate in the war-torn country.
However, all indications are that he quickly grew disillusioned with the reality on the battlefield.
"They just send the brothers to their death," he said in an audio message sent shortly before he died in July. The circumstances of his death are unclear.
According to Hamburg authorities, Florent was born in Cameroon and moved to Germany as a small child.