A policeman opened fire inside a police station in the southwestern Pakistani city of Quetta on Thursday, killing a suspect held on accusations of blasphemy, a local official said.

The slain man was identified as Syed Khan. Police said he had been arrested the day before, after officers snatched him from an enraged mob that claimed he had insulted Prophet Muhammad.

According to police official Mohammad Khurram, the officer involved in the fatal shooting has been arrested. Khurram did not provide further details.

Killings of suspects while in police custody are rare in Pakistan, where accusations of blasphemy — sometimes even just rumours — are common and often spark rioting and rampage by mobs that can escalate into lynching and killings.

Under Pakistan’s controversial blasphemy laws, anyone found guilty of insulting Islam or Islamic religious figures can be sentenced to death — though authorities have yet to carry out death sentences for blasphemy. In the case of Khan, the man killed on Thursday, local residents claimed he had used derogatory remarks against the prophet and went after him. After he was arrested, the mob surrounded the station, demanding police hand Khan back to them so they could kill him.

At one point, a man hurled a grenade at the station on Wednesday while a group of Islamists briefly blocked a key road in the city, demanding punishment for Khan.