PHILADELPHIA — On Monday, 17-year-old Santos Colon of Lindenwold, New Jersey, pleaded guilty to charges related to a plot to kill the Pope.

The teen had reportedly devised a plot to kill Pope Francis and detonate explosives during the Holy Father’s visit to Philadelphia for the World Meeting of Families in 2015.

The event was the last stop on Pope Francis’ six-day trip to the United States, during which he also visited New York City and Washington, D.C.

Hundreds of thousands of people were gathered at the Benjamin Franklin Parkway for the final papal Mass on Sunday, Sept. 27, 2015.

Colon was 15 years old at the time.

In the months leading up to the Pope’s visit, Colon thought he had made contact with a would-be sniper, when in fact he was engaging with an undercover FBI source, the Justice Department said in a statement.

“Colon engaged in target reconnaissance with an FBI confidential source and instructed the source to purchase materials to make explosive devices,” the department said.

FBI agents were able to quietly arrest Colon about two weeks before the Pope’s visit.

According to AFP news agency, the attack Colon was plotting was allegedly inspired by the Islamic State terrorist group, though it is unclear how connected he was to the group or whether he had made contact with any of its members.

Colon has pleaded guilty as an adult to one count of attempting to provide material support to terrorists. The charges filed against him as a juvenile have thus been dropped.

According to the Department of Justice, Colon faces a maximum of 15 years in prison and a fine of $250,000. A date has not yet been set for sentencing.

It is likely that Colon will be treated in a secure psychiatric facility before serving his sentence, if convicted.