The 22-year-old athlete was struck at El Tunco beach about an hour south of San Salvador on Friday, and efforts to revive her failed.
Her uncle Beto Diaz, a surfing coach, was with her when it happened.
Diaz said that after his niece arrived at the beach, she hugged a friend, a German surfer who was also there to practice. When they finished embracing, there was a roar, he told a local newspaper. “The friend was thrown by the force of the lightning strike. The board threw me back. Katherine died instantly,” Diaz said.
Observers said the storm had come up suddenly. “The sky was clear and it was an unforeseen storm that did not seem to carry much electrical intensity,” a witness told a Spanish-language newspaper, The Guardian reported.
The El Salvador Surf Federation issued a statement grieving “a great athlete who has represented our country. See you soon, great warrior. El Salvador is in mourning.”
Her brother Jose Diaz, president of the federation, wrote on Instagram: “We will always carry you in our hearts. God decided to take you now. We already miss you. Love forever little sister.”
The International Surfing Association — the world’s governing body for surfing — hailed Diaz as a standout surfer and “global ambassador of the sport” who “embodied the joy and energy that make surfing so special and dear to us all.”
Diaz started surfing at age 9.
Surfers in El Salvador are holding a “paddle out” Tuesday to honour her. Her funeral was held Sunday.