A 25-year-old man from South Carolina is in custody on an arrest warrant charging him with killing two men in Brockton last month. Guerry Hickman of Summerville, S.C., has been charged in the slayings of Tashawn Leslie and Tyrelle Baker, both 23, of Brockton, Plymouth District Attorney Timothy J. Cruz said in a statement. The two men were shot to death as they sat in a car Dec. 29. Cruz did not release any information on a motive for the killings. Hickman has been charged with two counts of murder, illegal possession of a firearm, and illegal possession of ammunition. He is currently in custody in North Charlestown, S.C.