SAN DIEGO -- Friends and family today were mourning a 50-year-old La Jolla man who became ill while surfing and died a short time later at the hospital.

William Joseph Ryan was surfing late Tuesday afternoon at Tourmaline Surfing Park in Pacific Beach when he suddenly slumped over on his board and slipped into the water, according to the San Diego County Medical Examiner's Office.

He attempted to get back on his board and told fellow surfers he was having trouble breathing, the Medical Examiner's Office reported.

San Diego lifeguards helped bring the man to shore, where they performed CPR and used a defibrillator until paramedics arrived and took Ryan to the hospital, lifeguard Lt. Andy Lerum told The San Diego Union-Tribune.

He died at Scripps Memorial Hospital in La Jolla at 6:15 p.m., according to the Medical Examiner's Office.

"It could have been a stroke, a seizure or a heart attack," Lerum told the newspaper.

An official cause of death was pending.