"The Canadian Broadcasting Corporation (CBC) reports Father Claude Grou, who serves as rector of the oratory, was rushed to a hospital while one man has been arrested, according to a statement from Céline Barbeau, a spokesperson for the oratory".
Montreal police say one individual has been placed under arrest and the priest is now in the hospital. He said the suspect didn't speak or call out during the attack.
The priest was allegedly stabbed after the man charged at him from behind the rectory, with a local witness describing the weapon simply as a "sharp object". By the time they arrived, the attacker had already been restrained by the oratory security staff, Caroline Chèvrefils, the spokesperson for the Montreal force, said.
An eyewitness said the attacker did not shout or say anything during the assault.
Plamondon said she saw people from the church tackle the alleged assailant to the ground; there were about 50 people attending mass.
Paramedics treated Grou at the scene and brought him to Montreal General Hospital to be treated for slash wounds to his belly.
Plamondon talked to Grou before he left the church, and told him "Saint Joseph protected you". The diocese of Montreal tweeted that he was in stable condition, and that "all of our prayers are with him". Now 77 years old, Grou has been at Saint Joseph's Oratory for more than 20 years, Lee reported.
"What a frightful attack at Saint Joseph's Oratory in Montreal this morning", Prime Minister Justin Trudeau tweeted. I am relieved to learn that the life of Father Claude grou, Rector of the @osjmr, is out of danger and that his condition is stable.
Though the priest suffered some injuries, he is not in danger and is expected to fully recover.
Montreal Mayor Valerie Plante tweeted: "What a terrible and inexcusable gesture that has no place in Montreal. On behalf of all Montrealers, I wish him a speedy recovery".
St. Joseph's Oratory is among Canada's largest churches, and pilgrims from all over the world are drawn to its domed roof and stunning architecture.
Montreal Archbishop Christian Lepine offered his support to Grou and those affected by the crime.