Another suspect involved in the killing of environmentalist and indigenous leader Berta Caceres was arrested Thursday, Honduran authorities said.
Elvin Heriberto Rapalo Orellana, also known as El Comanche, was the last person of interest wanted for allegedly carrying out the killing.
Ricardo Castro, head of the Central American country's criminal investigation unit, said Orellana could also be behind the shooting of Mexican activist Gustavo Castro who was with Caceres when the attack took place in March. Castro survived the attack.
Investigators are still working to find out who ordered the killing. Caceres, a Lenca Indian activist who won the 2015 Goldman Environmental Prize, was shot to death by three gunmen who broke in her home.
Caceres fought against construction of the Agua Zarca Dam on the Gualcarque River, a waterway the Lenca considered to be sacred. Dam opponents argued it would destroy the lives of hundreds of Lenca by cutting off the access to the river.
Among the other arrested suspects are an active duty army officer and a man who may have worked for Desarrollos Energeticos SA, also known as DESA.
Hidroeletrica Agua Zarca Co. officials - the management company behind DESA - denied any involvement, but confirmed one of the men involved in the case has worked for the company.
The Honduran government had assigned Caceres special protection because she expressed concerns about death threats by security people working for DESA.
The U.S. State Department condemned the shooting, calling on Honduras to carry out a transparent investigation. Washington offered to help bring the killers to justice.