A grade 12 student at a private college in Charsadda shot his college principal dead on Monday after being censured for skipping school to attend the November 2017 sit-in of religio-political parties in Islamabad's Faizabad area.
In a video acquired by DawnNews, the student, while being arrested, appeared to justify the murder saying he believed the college principal had committed blasphemy.
It was not immediately clear what prompted that charge.
"I have been taught... to kill... to not be afraid. Don't be afraid of disrespecting the one who" commits blasphemy, the student can be heard saying in the video in Pashto.
"You can kill me," he tells the arresting officers.
Shabqadar police said the suspect, Faheem, had fired multiple shots at his principal, Sareer, which proved fatal. District Police Officer (DPO) Charsadda Zahoor Afridi confirmed the incident.
The accused in the video seems to accept that he had fired six shots at the principal. "I am not afraid to kill," the student adds.
Police said the principal had earlier expressed his anger at Faheem over his being absent from college for three days.
Sources told DawnNews that the student had been angry that he was marked absent during the days he was attending the Faizabad sit-in.
Blasphemy is a highly sensitive issue in Pakistan, where even unproven allegations can stir mob violence and lynchings.
Last year, a mob in Abdul Wali Khan University Mardan beat up a student, Mashal Khan, to death after accusing him of blasphemy over social media.
The incident caused an outrage across the country, with calls for the blasphemy law to be amended. The investigation into Mashal's murder was concluded after a joint investigation team probing the case cleared the victim of all charges.
At least 65 people have been murdered by vigilantes over blasphemy allegations since 1990.