Matthew Warren, the son of evangelical megachurch pastor Rick Warren who committed suicide last week, killed himself with an unregistered gun he had bought online, the pastor said on Thursday.

"Someone on the Internet sold Matthew an unregistered gun. I pray he seeks God's forgiveness. I forgive him. #MATTHEW 6:15," the pastor tweeted, referencing a Biblical passage about the forgiveness of sins.

"If you forgive men when they sin against you, your Heavenly Father will forgive you. But if you don't...," Warren then tweeted, quoting the verse.

Since Matthew Warren, 27, died in his Mission Viejo, Calif., home on Friday, Rick Warren has taken to Twitter and Facebook to publicly grieve his son's death and spread awareness about mental illness. In an emotional letter he wrote to his Lake Forest, Calif.-based Saddleback Church community last week, Warren revealed that Matthew had been through years of "mental illness resulting in deep depression and suicidal thoughts."

It remained unclear how Matthew Warren had obtained a firearm. Gun registration documents are private in California, but permits to carry a concealed weapon are public records. The Orange County Sheriff’s Department told HuffPost reporter Anna Almendrala on Wednesday that Matthew Warren had never applied for a concealed weapon license.

Rick Warren's claim of the weapon's origin comes as Congress debates controversial gun-control legislation, including expanded background checks on gun sales. Warren did not reply to an email seeking comment on Thursday, but he has spoken previously about gun control and gun violence.

In a Fox News appearance after the Newtown, Conn., shooting in December, the pastor shared his views on what he called America's "culture of violence."

"There's a mental health angle that you have to deal with; I don't think we're taking care of those struggling with mental illness like we need to in America," he said. "There is the civil safety issue, which is gun control and these assault weapons -- they don't call them 'assault weapons' for nothing. There is the social issue ... students, by the time they're 18, they've maybe killed 10,000, 20,000 people on video games without any remorse for it."

UPDATE: 9:20 p.m. -- The Associated Press reports that the Orange County Sheriff's Department is trying to find the gun seller, but it won't be easy. The gun's serial number was scratched off, making it impossible to trace, spokesman Jim Amormino said.

"We can't tell if it's registered or not because the serial number is scratched off," Amormino said. "At one point in time, it may have been, but it's going to be impossible to find out."

It's illegal in California to buy a gun without a background check and purchasers are supposed to register their firearms. Defacing a gun's serial number is a federal offense.

Need help? In the U.S., call 1-800-273-8255 for the National Suicide Prevention Lifeline.

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  • Rick Warren

    Someone on the internet sold Matthew an unregistered gun.I pray he seeks God's forgiveness. I forgive him. #MATTHEW 6:15

  • Rick Warren

    You're most like Jesus when you pray for those who hurt you, "Father forgive them, for they don't know what they're doing."

  • Rick Warren

    We pray"Thy WILL be done on earth AS IT IS IN HEAVEN' since in heaven God's Will is done #always. On earth,it's done rarely

  • Rick Warren

    Kay and I are overwhelmed by your love, prayers, and kind words. You are all encouraging our #brokenhearts.

  • Rick Warren

    @KayWarren1 and I have never felt more loved. Your prayers are life-giving to us during our deepest grief. We love you back

  • Rick Warren

    Today we mourned Yom HaShoah Israel-6 million Holocaust deaths.Yesterday, Rwanda’s Day of Mourning-1 million Genocide deaths

  • Rick Warren

    Grieving is hard.Grieving as public figures,harder.Grieving while haters celebrate your pain,hardest.Your notes sustained us

  • Rick Warren

    We've known for years God would use us to fight mental illness but were protecting Matthew's right to share his own story.

  • Rick Warren

    Over the years,hundreds have written @KayWarren1 and me about mental illness in their families too.We've helped each other.

  • Rick Warren

    After 4 days, finally got to see my son’s body. He wasn't in it anymore. “Absent from the body is to be home with the Lord”

  • Rick Warren

    I've cried almost as many tears of joy as tears of grief in the last 48 hours, because you've loved @KayWarren1 and me,

  • Rick Warren

    Many ask “How can I help?” Help @KayWarren1 and me end the #stigma of mental illness! Join our team: http://t.co/B2LDPvl2Pl

  • Rick Warren

    "Carry each other's burdens. In this way you fulfill the law of Christ” Gal.6:2 (That law is love your neighbor as yourself)

  • Rick Warren

    "If you forgive men when they sin against you, your Heavenly Father will forgive you. But if you don't..." Matt.6:14-15

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