Legendary Mexican singer-songwriter Alberto Aguilera Valadez, known to millions of fans as Juan Gabriel, died Sunday near Los Angeles. He was 66. Details were not immediately confirmed. But noted Mexican journalist Joaquin Lopez Doriga said the iconic entertainer suffered a heart attack, just hours after performing to sold-out crowds in Los Angeles. A family statement was expected later Sunday. Mexican President Enrique Pena Nieto, writing Sunday on Twitter, mourned the death, calling Gabriel "one of the great musical icons of our country … a voice and a talent" that showcased Mexico and its music to the world. "Gone [too] soon, rest in peace." Gabriel — a six-time Grammy nominee known for his onstage flamboyance — first rose to fame in his homeland in the 1970s. In 1990, he became the first pop singer to perform at Mexico City's acclaimed Palace of Fine Arts, a venue until then reserved for classical musicians. A balladeer who sang of love and heartbreak, his recordings sold more than 100 million albums across Latin America, Spain and the Spanish speaking United States. One of his many hits, "Querida" ("Dear"), topped Mexico's pop music charts for an entire year. He was inducted into the Latin Music Hall of Fame in 1996, a year after being named Songwriter of the Year by the American Society of Composers, Authors and Publishers, known by the acronym ASCAP. He was awarded a star on the Hollywood Walk of Fame in 2009.