Actor James Darren, famous for his roles in Gidget and TV series such as T.J. Hooker and Star Trek: Deep Space Nine, has passed away at the age of 88.

TMZ reports that Darren died peacefully in his sleep at Cedars-Sinai Hospital in Los Angeles on Monday. The cause of death has not been confirmed yet, but his son, Jim Moret, mentioned that Darren had been dealing with heart issues and was under care at the hospital’s cardiac unit.

Darren had initially been admitted for an aortic valve replacement but was deemed too weak for the surgery. He was sent home but returned to the hospital shortly afterward.

Jim Moret shared, “I always thought he would pull through because he was so cool. He was always cool.”

Darren gained fame as a teen idol with his role as surfer Moondoggie in the 1959 film Gidget, reprising the role in two sequels: Gidget Goes Hawaiian and Gidget Goes to Rome. He also had a notable recurring role as Officer Jim Corrigan on T.J. Hooker, appearing in 66 episodes over four seasons.

In addition to his acting career, James Darren was a singer who performed the theme song for Gidget and directed episodes of Melrose Place, Beverly Hills, 90210, and The A-Team, among other shows.

Rest in peace, James Darren.