Dhaka , Bangladesh ( CNN ) Bangladesh authorities say they have arrested the prime suspect in the murder of American blogger Avijit Roy who was hacked to death on a Dhaka street last week . The person , Farabi Shafiur Rahman , had called for Avijit Roy 's death in numerous Facebook posts , according to Roy 's parents . And within minutes after the Thursday attack , Rahman posted photos of the crime scene , said Col. Ziaul Ahsan of Bangladesh 's elite anti-crime unit , the Rapid Action Battalion . In a Facebook comment last year , Rahman allegedly wrote , `` Avijit Roy lives in America . So it 's not possible to kill him now . But when he returns home , he will be killed then . '' In an earlier post , the same person wrote , `` It 's a Bengali Muslims holy duty to kill Avijit . '' Extremists resented Roy for openly and regularly criticizing religion in his blog . They threatened to kill him if he came home from the United States to visit . As usual , Roy defied the threats and departed his home in suburban Atlanta for Dhaka , where he appeared at a speaking engagement about his latest books -- one of them titled `` The Virus of Faith . '' He has written seven books in all . Roy was killed Thursday as he walked back from a book fair with his wife . Assailants plunged machetes and knives into Roy and his wife , killing him and leaving her bloodied and missing a finger . Witnesses said no one came to the couple 's aid as they were hacked down . Rahman , the man in custody , also allegedly posted threats against the owner of the online bookstore , Rokomari.com , forcing it to stop selling Roy 's books . And last year , he was detained -- then released -- for comments he allegedly made in support of the death of another blogger , Ahmed Rajib Haider . Like Roy , Haider too was hacked to death . He too had written critically about religion on his blog . CNN 's Ray Sanchez , Lonzo Cook , Greg Botelho , Farid Ahmed and John Couwels contributed to this report .
Police say the suspect posted photos of the crime scene . He also threatened Roy in social media posts , his family said .