Tito Jackson, one of the founding members of the legendary Jackson 5, passed away at the age of 70 on Sunday, Sept. 15.

According to initial reports from Entertainment Tonight, Steve Manning, a longtime Jackson family friend, revealed that Tito is believed to have suffered a heart attack while driving from New Mexico to Oklahoma. People magazine later confirmed the news with Tito’s nephew, Siggy Jackson.

At the time of writing, the official cause of death has not been determined.

Born Toriano Adaryll Jackson on October 15, 1953, in Gary, Indiana, Tito was an integral part of the Jackson family’s musical dynasty. He, along with his brothers Michael, Jermaine, Marlon, and Jackie, formed The Jackson 5 in the 1960s.

Tito’s rhythm guitar work and the harmonies of his brothers helped the group achieve meteoric success, culminating in their signing to Motown Records in 1968. Their debut single, “I Want You Back,” became an instant sensation, reaching No. 1 on the Billboard Hot 100, as did their subsequent hits “ABC” and “I’ll Be There.”

While his younger brother Michael often dominated the spotlight, Tito’s steady presence as a musician and performer was crucial to the band’s success. The Jackson 5’s debut album, Diana Ross Presents The Jackson 5 (1969), marked the beginning of their chart-topping career, with numerous tracks from that era becoming cultural staples.

In the 1970s, the group rebranded as The Jacksons after leaving Motown. Tito continued to perform and tour with his brothers through the 1980s, contributing to albums like Destiny and Triumph, both of which saw significant success on the Billboard 200 and R&B charts.

Beyond his work with The Jackson 5, Tito pursued a solo career, releasing his debut album Tito Time in 2016. His single “Get It Baby” reached No. 19 on the Billboard Adult R&B Songs chart.

Tito’s passing follows the deaths of his younger brother Michael Jackson in 2009 and their father Joe Jackson, the family patriarch and early manager of The Jackson 5, who passed away in 2018 at the age of 89. Michael’s sudden death in 2009 from acute propofol intoxication shocked the world, and his legacy as the King of Pop remains an indelible part of music history.

Tito is survived by his three sons, Taj, Taryll, and TJ, who formed their own musical group, 3T, and by his numerous grandchildren. His ex-wife Delores “Dee Dee” Martes passed away in 1994.

Billboard has reached out to Tito Jackson’s representatives for comment.