"I don't understand, all of our prayers go to his family and the Catholic community," said Mohammed Karabila.
Two armed men stormed the church during morning mass in Saint-Etienne-du-Rouvray, taking at least five people hostage before slitting the priest's throat and leaving another person in a critical condition.
The attackers, who the Islamic State group described as "soldiers" for the jihadist movement, were shot dead by police.
He said he and Jacques Hamel, who was in his eighties, had met on several occasions and had been part of an interfaith committee for the past 18 months.
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"We talked about religion and how to live together. It has been 18 months that civilians have been attacked, now they are attacking religious symbols, using our religion as a pretext. It is no longer possible," he said.
The town's mosque was inaugurated in 2000 on a piece of land gifted by the Catholic parish.
"It is a total shock, it brings back the pain," said his mother Latifa Ibn Ziaten, who launched an association to fight Islamic radicalisation after his death.
Like other towns around the city of Rouen, Saint-Etienne-du-Rouvray has a growing problem with radicalisation, she added.
"There are a lot of families that come and see me because their children are radicalising," she said.