Petaluma native Pierre Robert, one of the iconic voices of American rock radio and a longtime disc jockey on Philadelphia’s premier rock station WMMR-FM, died unexpectedly on Oct. 29, according to Rolling Stone magazine. He was 70.

Known for his big voice and even bigger personality, Robert’s on-air warmth and deep knowledge of rock made him popular not only with listeners, but also with the music legends he frequently interviewed, from Mick Jagger and Bono to Bon Jovi and the Foo Fighters.

A cause of death was not provided.

Of French heritage — his name is pronounced ro-BEAR — William Pierre Robert was born in Truckee. Within months of his birth his family moved to Petaluma, where his father Edouard Robert took a job as city attorney, a position he held for 18 years.

At Kings Beach in North Lake Tahoe, his parents built a small resort, which his mother Kathleen operated in the summers with help from her four children, including Pierre, who taught water skiing.

Robert graduated from Petaluma’s St. Vincent High School in 1973.

“He was a free spirit,” recalled childhood friend Tom Gaffey, manager of the Phoenix Theater. “Like many of us growing up in Petaluma in the ’60s and ’70s, he was strongly influenced by the rich Bay Area and post-British invasion music scene.”

Robert’s big break

After high school, Robert briefly attended college before dropping out to enroll in broadcasting school in San Francisco. He got his big break after landing a position as an unpaid intern at KSAN-FM — San Francisco’s pioneering progressive rock station — when he got to fill in for a DJ who didn’t show up for his 2 a.m. shift.

He soon got his own on-air shift on the station, but quit after KSAN switched to a country-and-western format.

With his 1972 VW Microbus “Minerva,” Robert decided to drive across the country to Philadelphia with a friend who had been accepted into medical school there.

A lifelong vegetarian, he took a job at a health food store, and began sending audition tapes to local radio stations. In 1981, he landed a job at WMMR as an evening DJ, eventually moving to the morning and then the midday slot.

For 44 years, Robert remained a beloved fixture at the station. Nationally, he became a pillar of the “progressive rock” format in which radio programming and song selection were driven exclusively by live DJs. A symbol of the undying spirit of rock, his radio playlists ranged from songs of the 1970s to the current day.

Ben Morrison, front man for the Bay Area band The Brothers Comatose, said his father Brad and Robert had been best friends since St. Vincent. Robert always hosted the band at his house and on his radio show when they passed through Philadelphia on tour.

“Walking into his house was like walking into the Rock and Roll Hall of Fame,” Morrison said, “full of photos of Pierre with the most amazing rock legends.”

The Brothers Comatose’s former bassist, local musician Giovanni Benedetti, said Robert was a great inspiration. “Other than Tom Gaffey, the only other person I’ve met who lived the true spirit of rock and roll was Pierre Robert.”

Known for his kindness, humility and humor, Robert liked to refer to his listeners as “good citizens,” displaying his own citizenship as an active fundraiser for AIDS organizations, environmental causes and animal rights.

Praise from Alice Cooper

Last year, he signed a new four-year contract to continue broadcasting at WMMR.

Following his unexpected death, condolences poured in from musicians, including Alice Cooper, who wrote, “Pierre wasn’t just a broadcaster. He was the rock and roll soul of this city.” Rolling Stone magazine anointed him “the last DJ.”

Robert is survived by two sisters, Clarisse and Suzanne, an older brother, Rene, and several nieces and nephews.