— -- The FBI has arrested two men -- one of them a current member of the Illinois National Guard -- for allegedly trying to launch attacks in the U.S. and overseas on behalf of ISIS, the brutal terrorist group wreaking havoc in Syria and Iraq, authorities said.
Army National Guard Specialist Hasan Edmonds, 22, was arrested at Chicago Midway International Airport as he was trying to fly to Egypt and ultimately join ISIS in Syria or Iraq, according to authorities. His cousin, Jonas Edmonds, 29, was arrested at his home in Aurora, Illinois, authorities said.
It was all the culmination of an FBI undercover operation, and both men had been under FBI surveillance for months, charging documents say.
Hasan Edmonds first came onto the FBI’s radar in late 2014, and the FBI investigation began with an undercover agent sending him a "friend request" over Facebook, according to the charging documents. That agent and the 22-year-old, who joined the Illinois National Guard about three years ago, began exchanging messages online. At the same time, Hasan Edmonds had allegedly been watching ISIS propaganda videos online.
In one message to the undercover FBI agent, Hasan Edmonda allegedly wrote: "I’d rather struggle and strive hard in the cause of Allah ... than sit back and live a 'comfortable' life. ... The [Islamic] State has been established and it is our duty to heed the call."
He allegedly noted that while he is already in an army of non-believers, "now I wish only to serve in the army of Allah alongside my true brothers."
"Either we will make it to [the Islamic State] or bring the flames of war to the heart of this land," he wrote that day, according to charging documents.
In later conversations with the undercover agent, Hasan Edmonds allegedly said his cousin -- who first brought ISIS to his attention -- was willing to conduct an attack inside the United States. Jonas Edmonds was then approached by another undercover FBI agent, and in the following days the group discussed ways of getting to Syria or Iraq.
By Monday, the three had allegedly finalized a plan: Hasan Edmonds would leave the United States to join ISIS, and he would give his cousin his military uniform. Jonas Edmonds would then use AK-47s and grenades to attack the military installation where his cousin trained, according to charging documents.
Jonas Edmonds said he wanted a "body count" as high as 150, the charging documents say.
Hasan Edmonds was arrested yesterday at Chicago's Midway airport. The FBI now has his luggage.
This case comes a week after a former U.S. Air Force veteran was indicted by federal authorities for allegedly trying to join ISIS.
Tairod Nathan Webster Pugh, 47, who is from New Jersey but had been living overseas for years, was secretly arrested two months ago after being deported back to the United States.
On his laptop, FBI agents allegedly discovered more than 180 jihadist propaganda videos and noticed he had been conducting online searches for such phrases as "borders controlled by Islamic state," "kobani border crossing," and "who controls kobani."
Last month, three New York City men were arrested on charges they allegedly conspired to join ISIS but also expressed willingness to carry out attacks on the terror group's behalf in the United States. The men had planned to travel to the Middle East and had also pledged to launch attacks in this country, including one on President Obama or planting a bomb in Coney Island, Brooklyn, federal officials said.
Over the past 18 months, about 30 people have been charged with joining terrorist groups in Syria and Iraq or trying to do so.
Get real-time updates as this story unfolds. To start, just "star" this story in ABC News' phone app. Download ABC News for iPhone here or ABC News for Android here.