The son of a police captain who was one of the first responders at the scene of the 2013 Boston Marathon bombing pleaded guilty Monday to plotting an ISIS-style attack.

Alexander Ciccolo faces 20 years in prison for plotting to use guns and homemade bombs to attack a college campus to support the Islamic State group. Sentencing has been scheduled for September.

Ciccolo was arrested in July 2015 after he received four guns he ordered from a person who was cooperating with the FBI, as Fox News previously reported. Boston police Capt. Robert Ciccolo tipped off authorities after his son said he wanted to join the Islamic State group.

Ciccolo, 25, initially was charged only with being a felon in possession of a firearm and stabbing a nurse in the head with a pen after he was brought to jail. But he later was indicted on attempting to provide material support to a foreign terrorist organization and attempting to use weapons of mass destruction.

Ciccolo, who went by the name Ali Al Amriki, pleaded guilty to all charges. His plea came a month before he was set to go on trial.

His lawyer did not immediately respond to an email seeking comment.

Prosecutors said Ciccolo told the person cooperating with authorities that he planned to commit acts of terrorism to support ISIS, including attacking an unidentified university using assault rifles and homemade bombs similar to the pressure cooker bombs used in the deadly 2013 Boston Marathon attack. The bombing at the marathon finish line killed three people and wounded more than 260 others.

Ciccolo was seen buying a pressure cooker shortly before his arrest, prosecutors said.

Prosecutors say agents found partially made Molotov cocktails in Ciccolo’s apartment after he was arrested. Investigators said posts on Ciccolo’s Facebook page included a photo of a dead American soldier that said “Thank you Islamic State!”

Federal authorities said Ciccolo’s case is a reminder that ‘homegrown’ radicalization remains a threat and that citizens must speak up when they become aware of a potential threat.

“Any material support of a terrorist organization threatens our national security, and had Mr. Ciccolo’s efforts to advance his agenda not been thwarted by the FBI’s Joint Terrorism Task Force, countless lives could have been lost in a lethal terrorist attack,” Harold Shaw, special agent in charge of the FBI’s Boston field office, said in a statement.

Ciccolo’s mother, Shelley MacInnes, told New England Public Radio last year that her son was “very compassionate” and “would not hurt a fly.” He converted to Islam a few years ago, MacInnes said.

The Associated Press contributed to this report.