Following the arrests of four California men on terrorism charges, the FBI warned the public not to underestimate home-grown extremist groups, as the plot was developed and serious, the Associated Press reported.


Americans Sohiel Omar Kabir, Ralph Deleon, Miguel Alejandro Santana Vidriales, and Arifeen David Gojali were all arrested over the weekend on charges they intended to provide material support to terrorists. The FBI alleged that Kabir sought to recruit the other three men to travel to Afghanistan for terrorism training so they could attack Americans living abroad.


"The main lesson learned is: Don't underestimate these groups," said FBI Special Agent David Bowdich. "This is a very serious case. I think ultimately the outcome was a success."


The men, the FBI said, were fairly well-organized and motivated even after they suspected one of their collaborators was a government informant.


Kabir, a naturalized U.S. Citizen and former member of the U.S. Air Force, was living in Afghanistan when he tried to recruit the three men. He met Deleon and Santana at a hookah bar and introduced them to the radical Islamist doctrine of American cleric Anwar al-Awlaki, who was killed by an American air strike last year in Yemen.


Santana and Deleon both expressed eagerness about plots to kill Americans. Santana told an undercover FBI agent that he was “excited” by the thought of murder. He told the same official that he had traveled to Mexico to learn how to fire guns and make explosives. Deleon reportedly told informant that he was hoping to be on the front lines in Afghanistan or use a C-4 explosive in an attack.


Court documents said that Gojali, 21-years-old, was recruited in September and declared himself willing to kill. His family, the AP reported, described him as being shy and vulnerable. He had met Deleon at his mosque, where Deleon was a popular figure and a compelling speaker, people said.


Kabir contacted the group using video calls from Afghanistan, where he promised he could introduce them to terrorists. They had purchased plane tickets to fly from Mexico City to Istanbul, at which point they would embark for Afghanistan, according to several reports.


Authorities said they learned about the group by tracking Kabir's travels and flagging violent messages Santana posted on extremist websites.


To avoid detection, the men wiped their Facebooks clean of any Islamist content and crafted cover stories. They planned to tell anyone who asked that they were attending Kabir's wedding.


According to an affidavit, Kabir intended to go on a suicide mission earlier this month, however he became sick and decided to wait for the group.


"They saw this as jihad. They saw this as their way to push out the aggressors," Bowdich said.