Castillo, a provincial radio host, was shot at least six times as he was having lunch at a local restaurant in the northern city of Virú, local press reports said.
Castillo, who hosted a news show on Ollantay Radio, was known for his criticism of local authorities, the regional press group Instituto Prensa y Sociedad (IPYS) said in a statement. News media reported that Castillo had received repeated death threats via phone.
Ollantay Radio was vandalized after Castillo had reported on a local politician, prompting its staff to seek police protection, IPYS said. The request was not granted.