A Kauai judge Wednesday convicted a 52-year-old Hanalei man who tried to rob a lunch wagon and used a knife to threaten a mainland firefighter who intervened.

William “Dukie” Kepia Puulei was convicted of second-degree robbery, first- and second-degree terroristic threatening and third-degree attempted extortion.

Prosecutors said the incident began when Puulei tried to take fruit from Sukothai North Shore Grill lunch wagon at the dry cave area of Haena Beach Park on Oct. 13.

Puulei threatened the lunch wagon owner and offered her “protection” from him doing anything in exchange for the food, said Circuit Judge Randal Valenciano, according to the Kauai Prosecutor’s Office.

Prosecutors said Puulei shouted at the woman, “Do you want protection?” and

“I am the local protection.”

A 36-year-old fireman from Washington state, who was visiting the beach with his family, tried to intervene. Puulei pulled a knife and told him, “Get back in your tourist car and leave my island. This is a local issue.”

The fireman asked Puulei to leave and Puulei walked away, prosecutors said. Police arrested him nearby and recovered a knife.

Puulei faces up to 15 years in prison when he is sentenced July 26.