Pastor Rick Warren -- Son Shot Himself

Pastor Rick Warrren's son used a gun to take his own life ... this according to the Orange County Coroner's office.

According to officials ... 27-year-old Matthew Warren's death Friday was from a self-inflicted gun shot wound ... that occurred inside his Mission Viejo home.

As TMZ previously reported ... Pastor Rick informed members of his Saddleback Valley Community Church Saturday about the suicide -- but gave no details -- except Warren had struggled with mental illness and depression for years.