A 21-year-old ISIS sympathizer planning to shoot up a 6,000 member megachurch in Detroit, Michigan has been arrested by authorities following a months-long investigation.

According to a report from the Guardian, Khalil Abu-Rayyan of Dearborn Heights is awaiting a hearing on Monday, having been investigated since May "regarding increasingly violent threats he has made to others about committing acts of terror and martyrdom - including brutal acts against police officers, churchgoers and others - on behalf of the foreign terrorist organization Islamic State of Iraq and Levant."

The Detroit News reports that undercover investigator who interacted with Abu-Rayyan on social media uncovered that the suspect had guns in his possession, and admitted that he "tried to shoot up a church one day."

"I bought a bunch of bullets. I practiced reloading and unloading," he said, according to the FBI.

A criminal complaint unsealed Thursday in U.S. District Court revealed that the church Abu-Rayyan was intending to target had a capacity of 6,000 members.

The complaint notes that Abu-Rayyan said that it would have been "easy" to fire shots at the church, but apparently did not carry out his plan at the time because his father discovered the gun, ammunition, and mask he had been planning to use.

"I tried to shoot up a church one day. I don't know the name of it, but it's close to my job. It's one of the biggest ones in Detroit. Ya, I had it planned out. I bought a bunch of bullets. I practiced a lot with it. I practiced reloading and unloading. But my dad searched my car one day and he found everything. He found the gun and the bullets and a mask I was going to wear," the ISIS supporter allegedly said, according to the affidavit.

"Honestly, I regret not doing it. If I can't do jihad in the Middle East, I would do my jihad over here," he added.

The court document also revealed that Abu-Rayyan used Twitter for "retweeting, liking and commenting" on IS propaganda since late 2014, including posts of a "video of a Jordanian fighter pilot being burned alive, men being thrown from a high rise building to execute them, the beheading of Christians in Egypt and news of ISIL victories."

Abu-Rayyan is not facing terror charges at this point, but faces federal charges of illegally having a firearm while using a controlled substance.

While the Detroit suburbs of Dearborn Heights and Dearborn have longstanding Arab and Muslim populations, US attorney Barbara McQuade told the Guardian that incidents like these are "an aberration" in the communities.

"We've not had any Isis cases arising out of [the area]," she said. "A lot of people vocally and visibly oppose Isis ... No one should make any conclusions about Dearborn or Dearborn Heights from this."

Muzammil Ahmed, board chairman for the Michigan Muslim Community Council, urged people not to jump to conclusions about what happened, but "wait for all of the facts to come in."

"Our thoughts are with our Christian friends and congregation that were threatened," he added. "We think that isolated acts like this, if they are indeed true, are an anomaly in this area."

A recent Gallup poll found that Americans are now more likely to name terrorism as the top issue facing the U.S. than to name any other issue -- including those that have typically topped the list recently, such as the economy and the government. About one in six Americans, 16%, now identify terrorism as the most important U.S. problem, up from just 3% in early November