QALQILIYA, WEST BANK — A mysterious blogger who set off an uproar in the Arab world by claiming he was God and hurling insults at the Prophet Muhammad is now behind bars — caught in a sting that used Facebook to track him down.

The case of the unlikely apostate, a shy barber from this backwater West Bank town, is highlighting the limits of tolerance in the Western-backed Palestinian Authority — and illustrating a new trend by authorities in the Arab world to mine social media for evidence.

Residents of Qalqiliya say they had no idea that Walid Husayin — the 26-year-old son of a Muslim scholar — was leading a double life.

Known as a quiet man who prayed with his family each Friday and spent his evenings working in his father's barbershop, Husayin was secretly posting anti-religion rants on the Internet during his free time.

Now, he faces a potential life prison sentence on heresy charges for "insulting the divine essence." Many in this conservative Muslim town say he should be killed for renouncing Islam, and even family members say he should remain behind bars for life.

"He should be burned to death," said Abdul-Latif Dahoud, a 35-year-old Qalqiliya resident. The execution should take place in public "to be an example to others," he added.

Over several years, Husayin is suspected of posting arguments in favor of atheism on English and Arabic blogs, where he described the God of Islam as having the attributes of a "primitive Bedouin." He called Islam a "blind faith that grows and takes over people's minds where there is irrationality and ignorance."

If that wasn't enough, he is also suspected of creating three Facebook groups in which he sarcastically declared himself God and ordered his followers, among other things, to smoke marijuana in verses that spoof the Muslim holy book, the Quran. At its peak, Husayin's Arabic-language blog had more than 70,000 visitors, overwhelmingly from Arab countries.

His Facebook groups elicited hundreds of angry comments, detailed death threats and the formation of more than a dozen Facebook groups against him, including once called "Fight the blasphemer who said 'I am God.'"

The outburst of anger reflects the feeling in the Muslim world that their faith is under mounting attack by the West. This sensitivity has periodically turned violent, such as the street protests that erupted in 2005 after cartoons mocking the Prophet Muhammad were published in Denmark or after Pope Benedict XVI suggested the Prophet Muhammad was evil the following year. The pope later retracted his comment.

Husayin is the first to be arrested in the West Bank for his religious views, said Tayseer Tamimi, the former chief Islamic judge in the area.

The Western-backed Palestinian Authority is among the more religiously liberal Arab governments in the region. It is dominated by secular elites and has frequently cracked down on hardline Muslims and activists connected to its conservative Islamic rival, Hamas.

Husayin's high public profile and prickly style, however, left authorities no choice but to take action.

Husayin used a fake name on his English and Arabic-language blogs and Facebook pages. After his mother discovered articles on atheism on his computer, she canceled his Internet connection in hopes that he would change his mind.

Instead, he began going to an Internet cafe — a move that turned out to be a costly mistake. The owner, Ahmed Abu-Asal, said the blogger aroused suspicion by spending up to seven hours a day in a corner booth. After several months, a cafe worker supplied captured snapshots of his Facebook pages to Palestinian intelligence officials.

Officials monitored him for several weeks and then arrested him on Oct. 31 as he sat in the cafe, said Abu-Asal.

Husayin's family has been devastated by the arrest. On a recent day, his father stood sadly in the family barber shop, cluttered with colorful towels and posters of men in outdated haircuts. He requested that a reporter not write about his son to avoid being publicly shamed.

Two cousins attributed the writings to depression, saying Husayin was desperate to find better work. Requesting anonymity because of the shame the incident, they said Husayin's mother wants him to remain in prison for life — both to restore the family's honor and to protect him from vigilantes.

The case is the second high-profile arrest connected in the West Bank connected to Facebook activity. In late September, a reporter for a news station sympathetic to Hamas was arrested and detained for more than a month after he was tagged in a Facebook image that insulted the Palestinian president.