Mr. Roy’s murder was heavy with symbolism. He had come to Dhaka for the publication of his new book at the Ekushey book fair, which takes place on the grounds of Dhaka University — historically, the center of the independence movement. The campus was where the Pakistani Army and allied militias chose to attack at the outset of its 1971 genocidal pogrom of minorities and pro-independence intellectuals. On Feb. 26, Mr. Roy had just left the university, and was on his way home, when machete-wielding assailants set upon him and his wife.

In 2013, the blogger Rajib Haider was stabbed to death a few feet from his home. His connection with the events of 1971 was not the university or the book fair, but the Shahbag movement, a protest incited by the war crimes trials of 2013. Mr. Haider had been prominent among those calling for the death penalty for the pro-Pakistan Islamists convicted of atrocities during the war of independence.

Mr. Rahman, the latest victim, was the quietest of the three. He was not particularly educated. He had not, as Mr. Roy had, published books and articles. He mostly wrote posts on Facebook. Why was he targeted? Why, among all the other bloggers, was his name the one that came up?

The police believe that his death was commissioned. Two madrasa students who were arrested at the scene have since confessed, according to reports, to having carried out the murder because of Mr. Rahman’s “writings against Islam.” (A total of four men have now been charged in connection with the killing.)

In the end, it was the digital technology used by the victims that may have brought about their deaths. Both Mr. Roy and Mr. Rahman had already received death threats via social media. Perhaps the person who engineered their deaths did a search for “Bangladeshi atheist blogger” to find a list of people who oppose fundamentalism, champion secularism or declare themselves to be atheist. The murderers admitted that they had never heard of Mr. Rahman or read his blog.