According to FBI records, the un-named source received more than $250,000 in payments from the government as well as immigration benefits.
"I would not consider that an extraordinary amount of money," FBI spokesman David Bowdich said at a news conference Tuesday. "The damage that could've been done by these individuals overseas will speak for itself."
According to the federal complaint, the four men charged planned to join al-Qaida and kill or kidnap Americans abroad.
The complaint describes how the four men planned to travel to Afghanistan to join the Taliban and eventually al-Qaida. The confidential source was present for many of their meetings, participated in internet video chats or calls and appears to have played along as if he, too, wanted to join Al-Qaida.
"The CS is an individual who has been reporting to the FBI full-time for over 4.5 years and has provided credible and reliable information in the past," according to the complaint. "The CS was previously convicted of trafficking in pseudoephedrine."
The four arrested are Sohiel Omar Kabir, 34, an Afghanistan native and former resident of Pomona; Ralph Deleon, 23, of Ontario and a native of the Philippines; Miguel Alejandro Santana Vidriales 21, of Upland; and Arifeen David Gojali, 21, of Riverside, a United States citizen.
The complaint, filed in U.S. District Court in the Central District of California, details the group's activities over the past year as witnessed by the confidential source.
In September, the source, Deleon and Santana went to shooting ranges in Los Angeles "to practice."
Earlier, Santana had told the confidential source that he had a friend who worked at a local gun range that did not ask for anyone's identity.
On their way to a shooting range, the informant "observed that Deleon and Santana were excited about the prospect of rewards from being a martyr," according to the complaint.
"While at the range, Santana selected an M4 assault rifle for them to shoot. While Santana and Deleon shot the rifle, they took turns video-recording each other. Deleon mentioned to the CS that they will reap heavenly rewards for going to the shooting range. Santana and Deleon also wanted to shoot a handgun and rented a Glock pistol. When finished, Deleon suggested they keep their paper targets, which they did."
During a separate conversation, the confidential source asked Deleon what group they would join if they went to Afghanistan.
"Deleon said `AQ' or the Taliban. Deleon said he had been doing research on the Taliban and thought the Taliban was fighting for the right cause," according to the complaint.
Santana said he preferred to go to Afghanistan because he was under the impression the military bases there could easily be ambushed "from every direction."
"The CS asked Deleon and Santana if they had thought about how it would feel to kill someone. Deleon said he had thought about it and `wouldn't have a problem if it's, it's for Allah'," according to the complaint. "Santana said he would not have a problem with it and `the more I think about it the more it excites me."'
The informant was told they would be fighting American, British, U.N. and Israeli troops.
During a conversation about suicide bombers, "Deleon told the CS that he learned from Kabir that there were scores of men in Afghanistan waiting for their chance to die as a suicide bomber."