Editor's note: Watch Part 2 of Drew Griffin's special investigative report about Walid Shoebat Thursday on AC360° beginning at 10pm ET.

Rapid City, South Dakota (CNN) - Walid Shoebat had a blunt message for the roughly 300 South Dakota police officers and sheriff's deputies who gathered to hear him warn about the dangers of Islamic radicalism.

Terrorism and Islam are inseparable, he tells them. All U.S. mosques should be under scrutiny.

"All Islamic organizations in America should be the No. 1 enemy. All of them," he says.

It's a message Shoebat is selling based on his own background as a Palestinian-American convert to conservative Christianity. Born in the West Bank, the son of an American mother, he says he was a Palestinian Liberation Organization terrorist in his youth who helped firebomb an Israeli bank in Bethlehem and spent time in an Israeli jail.

That billing helps him land speaking engagements like a May event in Rapid City - a forum put on by the state Office of Homeland Security, which paid Shoebat $5,000 for the appearance. He's a darling on the church and university lecture circuit, with his speeches, books and video sales bringing in $500,000-plus in 2009, according to tax records.

"Being an ex-terrorist myself is to understand the mindset of a terrorist," Shoebat told CNN's "Anderson Cooper 360."

But CNN reporters in the United States, Israel and the Palestinian territories found no evidence that would support that biography. Neither Shoebat nor his business partner provided any proof of Shoebat's involvement in terrorism, despite repeated requests.

Back in his hometown of Beit Sahour, outside Bethlehem, relatives say they can't understand how Shoebat could turn so roundly on his family and his faith.

"I have never heard anything about Walid being a mujahedeen or a terrorist," said Daood Shoebat, who says he is Walid Shoebat's fourth cousin. "He claims this for his own personal reasons."