(CNN) There is a void in the house where Avijit Roy once lived. Nearly a year after his shocking murder , the feeling of emptiness is palpable for first-time visitors stepping into his home.

His widow, Rafida Ahmed, says she avoids the small book-strewn study where the couple once worked, shoulder to shoulder at a pair of desks, writing and editing Roy's manuscripts.

"This is where Avijit spent more than half of his life," she says, shaking her head. "I try not to come here."

The desk to the right is where Ahmed's husband Avijit Roy used to work in their shared office.

In fact, Ahmed has removed photos of her slain husband from the family's two-story home, which sits in a sleepy suburb on the outskirts of Atlanta.

The neighborhood's tidy lawns and mailboxes adorned with red flags are a world away from the dark patch of sidewalk in Bangladesh where, on the night of February 26, 2015, attackers armed with machetes pounced on the couple.

That night, Ahmed and Roy had just walked out of a book fair where the writer was promoting one of his books.

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Ahmed, a naturalized American citizen originally born in Bangladesh, barely survived the vicious attack.

"I had four machete stabs on my head," she explains. "My thumb was sliced off," she adds, holding up her mutilated left hand. "They hit me in other places of my body too."

A year later, still in recovery from the physical and psychological trauma of that terrible night, Ahmed says there is no question why she and her husband were targeted.

"Criticizing Islam is becoming a very big crime -- a sin -- in Bangladesh," she explains.

Few neighbors in this corner of the U.S. probably knew that Roy was an outspoken champion of atheist thought back in the country of his birth.

As his stepdaughter puts it, Roy lived something of a double life in the U.S. "Though my dad worked as a Java programmer during the day, he was a Bengali writer when he came home," writes Trisha Ahmed Hoque.

Roy's daughter says her father led a double life in the U.S. as a programmer and a Bengali writer.

And he was prolific, authoring eight books, editing two more books and managing a website that promoted "freethinking," an atheist intellectual movement that frequently challenged organized religion.

In one of his books, titled " The Virus of Faith ," Roy compares religious extremism to a highly contagious virus. The book infuriated some Islamists.

In a follow-up article published by an atheist group called Secular Humanism , Roy wrote "the death threats started flowing to my e-mail inbox on a regular basis. I suddenly found myself a target of militant Islamists and terrorists."

His wife was aware that he had received threats. "Our mistake, we did not take it seriously," says Ahmed. "When we went to Bangladesh, we didn't think this was a real threat."

But the assassination of Roy was not a one-off event.

Series of murders

In the following months, attackers carried out similar machete murders, killing at least four other writers and publishers of secular thought.

The most recent assault on October 31 resulted in the death of publisher and blogger Faisal Arefin Dipan, whose company published Roy's book "Virus of Faith." Assailants cut Dipan down in his office.

The body of Bangladeshi publisher Faisal Arefin Dipan lies at the Dhaka medical college hospital.

"It was almost like a one-a-month kind of deal," Ahmed says, of the killings. "They have a free pass. The impunity has gotten to a point that they know they can get away with anything."

In 2015, the freedom of press watchdog Committee to Protect Journalists listed Bangladesh as 12th in the world on its Global Impunity Index highlighting countries "where journalists are slain and the killers go free."

Police in Bangladesh insist they are doing their best to protect writers.

"I think the situation has become safer now," Joint Police Commissioner Monirul Islam told CNN this month.

The commissioner says at least eight suspects have been arrested in connection with the Avijit Roy murder. None of them have appeared in court yet because the case is still under investigation.

Islam argues that some of the writers who were murdered -- including Roy -- did not inform authorities ahead of time that they had received threats.

"So how could we provide security for them?" he asks.

Claims and confessions

Claims of responsibility for the atheist blogger murders emerged on social media from Al Qaeda in the Indian Subcontinent.

"These secular and atheist publishers waged war against the religion of Islam in every possible ways [sic]," the group wrote, in a statement archived by SITE Intelligence Group, a jihadi monitoring organization.

"One of them also published books in support of homosexuality. They tried to drag the partially-educated Muslim youth who are deprived of the Islamic knowledge into the vicious circle of atheists."

The Bangladeshi government has vigorously rejected warnings from U.S. intelligence that ISIS is trying to attract recruits in the South Asian country.

Instead, Bangladeshi officials insist the blogger murders, and a surge in killings in recent months of visiting foreigners and members of Bangladesh's Hindu, Christian and Shi'ite religious minorities are the work of homegrown extremist groups.

"We have made arrests on each and every so-called ISIS-claimed attack," says Islam, the Bangladesh police official.

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"The attackers have confessed their crimes in court. They have also confessed being a Jamaatul Mujahedin Bangladesh member, and denied any linkage with ISIS."

Islam describes Jamaatul Mujahedin Bangladesh, or JMB, to be the region's newest, biggest player when it comes to violent Islamist groups.

But the professed crackdown by the police has not translated to a reduction in threats against secularist writers.

Daily threats and defiance

Maruf Rasul, a secularist writer based in Dhaka, says he receives threatening phone calls from Islamists on a daily basis.

"They say 'hello atheist.' Some use very vulgar words, some of them pray to Allah, some say 'I will buy you a coffin," he tells CNN.

The 28-year-old writer says he now lives in fear, constantly looking over his shoulder when stepping out into the city. Many of his fellow bloggers are trying to flee the country.

"I will not leave the country because it's a fight," the writer announces defiantly.

"This country should be a secular country. This country should be a democratic country. It is not an Islamic country," he argues.

"I have the right to ask questions about anything, about religion... I have the right to express my thoughts. If you don't like it, don't read it!"

Islamic country, with principle of secularism

Bangladesh is a majority Muslim country, with a sizable Hindu religious minority. The constitution defines Islam as the state religion. But the document also includes a clause promising to defend the "principle of secularism."

At the annual book fair in the capital this year, supporters displayed portraits of some of the victims of the blogger attacks. One booth displayed the framed papers of the slain publisher Dipan , the pages stained with his blood.

Echoes of the violence in Bangladesh are still being felt a world away in the U.S.

"I had to learn how to type without my thumb," says Ahmed. She says the loss of one of her digits is minimal compared to the crippling headaches and emotional and psychological pain she is still coping with.

Rafida Ahmed has learned to type without a thumb after the brutal attack last year.

The FBI has advised Ahmed and her daughter on safety precautions to protect against the threat of further possible attacks.

Ahmed has taken a leave of absence from her job as a senior director at a credit bureau. She spends much of her time trying to help endangered writers escape Bangladesh.

"There is no protection for these people," she says.

Despite the deadly setbacks, the widow of Avijit Roy argues that the murders have helped unite Bangladeshi "freethinkers."

Her husband's blog MuktaMona has begun publishing his books online for free. "We will come out as a much louder voice," she says, through Internet distribution.

But the explosion of social media has also provided platforms for religious extremists on the opposite side of the ideological divide to network and organize.

"If their voices get louder, in the intellectual way... we would really welcome that," she insists. "We would work on healthy debates. [But] when we disagree, we don't go out with machetes and kill people. That's the difference."