The congregation of Saddleback Church is mourning the loss of Matthew Warren, 27, who committed suicide on Friday.

Matthew was the youngest child of Purpose Driven author and Saddleback Pastor, Rick Warren and wife Kay.

A coroner report said he died from a self-inflicted gunshot wound at his home in Mission Viejo after a long battle with mental illness.

Family, friends and church members filled Saddleback Valley Community Church, in Lake Forest, California, on Sunday.

Tom Holladay, teaching pastor at the mega church, said at the 9am worship service that the congregation would face the tragedy together as a "church family".

The service was not attended by Rick or Kay.

Holladay, who is married to Rick Warren's sister, Chaundel, led a prayer for Warren and his wife, Kay, and their two other children.

In a statement on Saturday morning, Rick Warren said Matthew had battled depression for much of his life, and stated, "Today after a fun evening together with Kay and me, in a momentary wave of despair at his home, he took his own life."

He described Matthew as a "kind, gentle and compassionate man" with a "brilliant intellect" who was sensitive to the needs of others.

"Kay and I often marvelled at his courage to keep moving in spite of his relentless pain. I'll never forget how, many years ago, after another approach had failed to give relief, Matthew said, 'Dad, I know I'm going to heaven. Why can't I just die and end this pain?' But he kept going for another decade."

Despite that, he said, his son lived for another decade, during which he often reached out to help others.

Pastor Warren has asked for prayers for the family during this difficult time.