UPLAND, Calif. (AP) — Three of the young men swept up in a federal terrorism probe grew up in the Southern California suburbs where they played pick-up basketball, ran for homecoming court and sparred in video games with neighborhood kids — a far cry from the wannabe terrorists described by the FBI.

Two of the men converted to Islam less than two years ago and the third, an American-born Vietnamese Muslim, drifted into their orbit as recently as September after a game of paintball. He also is an unemployed high school dropout and new father.

The rapid evolution from suburban teen to aspiring jihadist alleged in court documents blindsided family members, but experts who study homegrown terrorism said the case highlights the susceptibility of new converts to radicalization, particularly among the young.

Conversion to Islam requires just a single statement of faith, but the newly faithful must then choose among a universe of competing interpretations of Islam, many overtly political and easily available on the Internet.

"To convert to Islam you just have to make one statement of faith: 'There is no God but God, and Muhammad is his messenger.' But these people did that and then they feel they are Muslim," said Muhamad Ali, an assistant professor at the University of California, Riverside, and an expert in Islamic studies.

"They might pray five times a day, they might fast, but they don't see Islam in a comprehensive way. Education and understanding are critical and one of the challenges in the United States is to make sure that these converts are in the right hands."

According to court documents, the four men arrested late last week found trouble from the start.

Two of the members of what the FBI called an extremist network — Miguel Alejandro Santana Vidriales, 21, and Ralph Deleon, 23 — converted after meeting Sohiel Omar Kabir in an Ontario, Calif., hookah bar. The naturalized U.S. citizen from Afghanistan introduced them to the radical Islamist doctrine of the U.S.-born extremist cleric Anwar al-Awlaki, who was killed last year in an American airstrike in Yemen, according to court files unsealed this week.

Kabir, 34, later returned to Afghanistan but continued to give direction to the Southern California men on Skype. He was taken into custody last weekend.

The fourth defendant, 21-year-old Arifeen David Gojali, joined the group in September after they played paintball together to sharpen their shooting skills, according to court documents.

The father of a baby girl had moved out of his parents' home two months ago and drifted away as he fell under the sway of Deleon, who was a charismatic and popular worshipper at the mosque the two attended, Gojali's younger sister told The Associated Press.

His family didn't know of his arrest until news reports earlier this week and was shocked at what they heard, said the sister, 18, who requested anonymity because she did not want to be associated with the alleged crimes.

"What a lot of the news channels are saying is the first time I'm hearing about it and the first time my family's hearing about it," she said.

All four men are facing charges of providing material support to terrorists, which can carry a maximum 15-year prison sentence.

Authorities won't say how the investigation began, but at least two members of the group shared their beliefs on Facebook and held Skype phone calls with Kabir — all of which was recorded by an FBI informant or captured by agents monitoring their activity.

Covert FBI agents had conversations with Santana online, where he expressed his support of jihad and desire to join al-Qaida, authorities said. Continued...