MEDAN, INDONESIA — Indonesian police are investigating a possible ISIS-related attack after a teen attempted to bomb a church in Medan, North Sumatra.

On Sunday, Ivan Armadi Hasugian sat among the worshippers during morning mass at St. Joseph Catholic Church, reports the Jakarta Post.

He had a black backpack with him. Hidden inside was a homemade bomb assembled from a battery and pipe.

The 17-year-old detonated his device in the middle of service, but instead of a huge blast, the device only gave off smoke and sparks. He stood up abruptly, and after taking an axe from his bag, charged at the priest on the pulpit.

The Straits Times reports that the priest, 60-year-old Albert Pandiangan, received a slight wound on his left arm before members of the congregation managed to restrain his attacker. He is now in police custody.

Hasugian reportedly confessed that he was ordered to carry out the bombing. Authorities believe he is affiliated with the Islamic State, after a piece of paper bearing the terror group’s logo was found in his wallet.

Police do not believe he was working alone, and are currently hunting down his accomplices.