TEGUCIGALPA, Honduras — Honduran indigenous leader Berta Caceres, who won the 2015 Goldman Environmental Prize for her role in fighting a dam project, was shot dead Thursday by multiple gunmen who broke into her home, authorities said.

Caceres, a 40-year-old Lenca Indian activist, had previously complained of receiving death threats from police, soldiers and local landowners because of her work.

Tomas Membreno, a member of her group, the Indian Council of People’s Organizations of Honduras, said at least two assailants broke into a home and shot Caceres to death early Thursday in the town of La Esperanza.

“Honduras has lost a brave and committed social activist,” Membreno said in a statement.

The killing appeared to be targeted: A Mexican rights activist at the house was only slightly wounded in the attack, but Caceres’s body had four gunshot wounds.

Police said they had detained a suspect, but did not identify the person.

People hold photos of slain Honduran environmentalist and indigenous leader Berta Caceres at the coroner’s office in Tegucigalpa on Thursday. The mother of four was 40.

People hold photos of slain Honduran environmentalist and indigenous leader Berta Caceres at the coroner’s office in Tegucigalpa on Thursday. The mother of four was 40. The Associated Press

Caceres, a mother of four, led opposition to a proposed dam on the Gualcarque river, considered sacred by the Lencas.

Many of the project’s backers have largely abandoned building plans.

President Juan Orlando Hernandez wrote in his Twitter account that “this act has caused mourning among all Hondurans.”

His chief of staff, Jorge Alcerro, said “the president has instructed all government security forces to use all means to find the killers.”

Alcerro said Caceres was supposed to be receiving special protection because of the death threats, but did not explain why there were no police protecting her when she was killed.

Security Minister Julian Pacheco said police had initially been assigned to protective detail but Caceres asked for them to be withdrawn because they bothered her.