Prakash Singh, a retired police officer and a key architect of police reforms, told the BBC the killings were "entirely avoidable". "Abundant caution should be taken when people in custody are being taken to the court or the scene of the crime," he said. "They should be secured, handcuffed and properly searched before they are taken out. All kinds of things can happen if the police are not careful." But Mr Singh said it was too early to say if the incident was an extrajudicial killing - known popularly in India as an "encounter killing".