According to the complaint, Osadzinski designed a process that uses a computer script to make Isis propaganda easier to access and disseminate on a social media platform, bypassing preventive code that routinely removes Isis content because of the violent nature of the materials.

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The complaint, however, did not identify the social media platform, saying only that it was a mobile and desktop messaging application.

Osadzinski earlier this year shared his script – and instructions for how to use it – with individuals whom he believed to be Isis supporters and members of pro-Isis media organisations, the complaint says.

Those individuals were actually covert FBI employees and a person working with them.

Agents began tracking him last June, when Osadzinski posted in a pro-Isis chat room, according to the complaint. Osadzinski, unsolicited, began reaching out to pro-Isis media platforms and offering to help translate videos from Arabic to English.

“I know English well. If you need help tell me …” he wrote to an agent in Arabic on the social media platform.

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Osadzinski later told an agent that he had done the English voice-over for a pro-Isis video, as well as translations for others. The agent who reviewed the video voice-over concluded that the narrator spoke English with an American accent.

Osadzinski continued to communicate with at least four undercover agents over the months-long investigation, despite telling them that he knew the FBI was monitoring him.

“Once I get my gun and explosive belt, the mukhabarat will never get me,” Osadzinski wrote to an agent, using the Arabic word for state security and intelligence services.

Osadzinski told one agent that learning computer skills was “very useful for jihad”, according to the complaint. At one point, Osadzinski sent an agent a screenshot of a social media channel that he had created, which appeared to contain thousands of photos, videos, files, audio clips and links.

Osadzinski slowly revealed that he kept pro-Isis materials in his 13th-floor flat.

He sent one agent a photo of a large poster with Quranic verses written on it, telling the agent that he had printed it out at the university library. Osadzinski later sent another photo, of an Isis flag lying on his desktop computer.

According to the complaint, Osadzinski appeared to be inspired by the 2009 attack at Fort Hood, Texas, when an Army psychiatrist fatally shot 13 people in the deadliest mass shooting on a US military base.

The shooter had shouted “Allahu akbar” (“God is greatest” in Arabic) during the attack, later calling it retaliation for US wars in the Muslim world.

After the death of Isis leader Abu Bakr al-Baghdadi last month, Osadzinski, unprompted, sent a message to one agent announcing his allegiance to the new leader of Isis.

In February, an information technology professional who had met Osadzinski through his computer science studies called the student under the guise of discussing computer science programmes. The source befriended Osadzinski and falsely told him that he, too, was an Isis supporter. The source met with Osadzinski in person five times.

The two became close. Osadzinski told the source about his plans to meet up with his prospective spouse in Indonesia. He detailed his research into the FBI agent that he suspected was tailing him, revealing that he knew details about the agent’s father.

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Osadzinski also showed the source screenshots of messages he had sent to individuals in Chechnya, instructing them on how to use the code.

According to the complaint, the confidential source has been involved with multiple FBI investigations since 2013 and has been paid around US$350,000.

DePaul University in Chicago confirmed that Osadzinski is a currently enrolled student. “We recognise the seriousness of the charges and would cooperate with authorities if contacted,” a university representative said.

According to Osadzinski’s LinkedIn profile, he currently works in IT at DePaul. In the past, he worked as a software tester at software developer Cylance Inc and as an Electronic Sales Associate at Target, his profile says. He lists skills in Java and Python programming languages.

Osadzinski is expected to appear for a detention hearing on Friday.