Johannesburg - A police constable has handed himself to police after allegedly shooting dead a woman outside a tavern in Vosman, near Witbank, Mpumalanga police said on Monday.Preliminary investigations suggested the 33-year-old constable was off duty and visiting a tavern around 02:00 on Sunday, when he and another patron had an argument, police spokesperson Leonard Hlathi said in a statement.They agreed to take their disagreement outside, but when the constable went outside the other man did not follow. A 22-year-old woman, however, followed the policeman out. He allegedly shot her.Hlathi said the motive for the killing was not yet clear."The police constable has since handed himself over to Vosman police station and the case is being investigated by the Independent Police Investigative Directorate."Acting provincial police commissioner Major General Meshack Nogwanya condemned the killing. He said it was unacceptable and unlawful for a police official to take a firearm into a tavern."I wish to take this opportunity to send a stern warning to members of SA Police Service to behave in accordance with the code of conduct."