Story highlights Police say the suspect posted photos of the crime scene

He also threatened Roy in social media posts, his family said

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."

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