It is claimed that the officers tortured a man to death in 1983 in a city police station.

tortured 是动词 torture 的过去式形式。torture 的意思是"拷打、折磨"，指通过施加身体或精神上的痛苦来迫使某人屈服或招供。在句中表示警官们过去对某人实施了酷刑。