Glenn “Shemy” Schembechler, the son of legendary Michigan coach Bo Schembechler, resigned from his position as assistant director of football recruiting with the Wolverines last month after his social media revealed Schembechler “liking” racist tweets.

Michigan coach Jim Harbaugh spoke with reporters at a football camp at Wayne State University on Thursday and cited an error in the vetting process regarding the hire.

“Once I became aware of things that were offensive—offensive to me, offensive to other members of our team—[we acted],” Harbaugh said. “We didn’t want that mindset around.”

The 53-year-old Schembechler stepped down just three days after he was hired by Harbaugh.

“I read the report myself. We have a company that vets that social media, and they came back and [cleared him]. We’ve got a new company doing that, but they’ve got to be better. I’ll take responsibility for that,” Harbaugh added. “If somebody can find that in a day, then we have to be better ourselves. I’ve known Shemy for a long time, but there’s no sacred cows. It’s not who we are. It’s not us.”

A Michigan spokesperson told ESPN that the athletic department has changed the vendor that handles HR background checks following the Schembechler situation.

“We currently utilize two background checks for vetting athletic department staff, but are reevaluating that process that process moving forward,” associate AD for football communications, David Ablauf told ESPN.

Schembechler has since deactivated his Twitter account.