The priest was killed earlier in the day, with the police immediately excluding terrorism as the suspect's motivation. The suspect — who was taken into care by a Catholic community as he awaited trial after setting a cathedral in Nantes on fire last year — reportedly turned himself in earlier on Monday.
The Rwandan refugee was released, as his psychological condition was deemed incompatible with arrest, the broadcaster said.
The suspect reportedly underwent treatment in a psychiatric hospital from late June to late July.