A Twitter user operating under the handle "@SoCalMAB" -- an account that has since been deleted -- fired off several disturbing tweets over the weekend during national protests.

In some, the user -- whose account had a profile picture of former USC receiver Michael Pittman standing next to a female fan -- advocated to "shoot the protestors."

The tweets got so nasty ... Pittman himself felt the need to intervene, telling the account to remove his picture from the profile ASAP.

"@SoCalMAB if you truly believe the things you have said, I politely ask you to take me out of your profile picture," the Indianapolis Colts rookie said. "This is disappointing, I know my true Trojan family would never. In times like this, it is important for us to stand together."

Bohn said on Monday the school launched an investigation into the tweets after they were made aware of the disturbing content ... and after they identified the fan as a school booster, they dropped the hammer.

"Following an immediate investigation into the matter, we informed the individual that their season ticket and Trojan Athletic Fund membership privileges have been revoked and their payments will be promptly returned," Bohn said. "Their account has been flagged in our system to prevent future purchases."

Bohn added, "Thank you to the USC community for helping us identify this individual so that we could move swiftly to terminate our relationship. We stand in solidarity with the Black community."