Chavo Guerrero Sr., one of the pro wrestling world’s most respected performers, has died after a short battle with liver cancer. He was 68.

Guerrero’s son and namesake, Chavo Guerrero Jr., who also wrestled with WWE, made the announcement on Saturday.

“Today the world lost a true rebel,” Guerrero Jr. wrote of his father on Instagram, revealing Guerrero had been fighting his illness for just one month since being diagnosed with the disease in early January.

Known as Chavo Classic to WWE fans, Guerrero Sr. became popular as one of “Rowdy” Roddy Piper’s biggest rivals in the business.

Guerrero Sr. was a 15-time NWA Americas heavyweight champion for NWA Hollywood Wrestling, before coming to WWE, where he became the oldest competitor ever to win the original Cruiserweight Championship title. He was in his fifties at the time.

Guerrero, whose father Gory and brothers Mando, Hector and Eddie were also pro wrestlers, last made a high-profile appearance in the squared circle last year on Lucha Underground, a televised pro wrestling program produced by famed director Robert Rodriguez. In the bit, Guerrero turns on his son to help rival Rey Mysterio Jr.

As news broke of Guerrero Sr.’s death, the pro wrestling world offered its condolences.