Story highlights The professor "was neither a blogger nor an anti-Islamic campaigner," police say

ISIS has claimed responsibility for the killing

The English professor was waiting for a bus near his home when he was stabbed

Dhaka, Bangladesh (CNN) Bangladeshi police have detained a university student in connection with the hacking death of a professor. But why the teacher was stabbed in the neck remains unclear.

Authorities earlier said the student had been arrested but later clarified their report.

"We haven't arrested him or brought any charges against him yet," Rajshahi police Commissioner Mohammad Shamsuddin said Sunday. "He is a suspect, and we've taken him to our custody for interrogation."

The slain professor, 58-year-old Rezaul Karim Siddique, taught English at Rajshahi University.

He was waiting for a bus to take him to campus Saturday when he was attacked from behind and stabbed in the neck, police said.

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