The general counsels of the International Brotherhood of Teamsters (IBT) and AFL-CIO have asked the Institute of Human Rights at the Jesuit Central American University in San Salvador to conduct a full independent investigation of murdered Teamster leader Gilberto Soto back in November in El Salvador.

Both organizations believe the crime is related to Soto’s efforts to organize Central American port truckers.

Soto was shot in the back and killed on Nov. 5 while making a cell phone call outside his mother’s house in Usulutan, El Salvador, said IBT. He was in Central America meeting with port container truck drivers from El Salvador, Honduras and Nicaragua with the help of the London-based International Transport Workers Federation in an effort to build a “solidarity network” linking the unions in order to represent workers employed by Denmark-based A.P. Moller Maersk, the world’s largest steamship line.

IBT said that El Salvadoran officials have wrongly classified Soto’s death as a “common crime” and added that they “have lost all confidence in the state investigation” of Soto’s slaying primarily because the police never pursued the theory that his union activities might have been the motive behind his murder.