Will Cain joins First Take and says the threatening letter sent to Texas A&M coach Kevin Sumlin's home is embarrassing for the state of Texas. (0:58)

Texas A&M coach Kevin Sumlin received racist hate mail at his home this week, his wife said on Twitter.

Charlene Sumlin tweeted a picture of the letter Thursday afternoon. It reads: "You suck as a coach! You're a n----- and can't win! Please get lost! Or else."

She wrote in the tweet: "People of 2017: please tell me how any part of this is ok. And to the sender: did it occur to you that a child may open it? #orelseWHAT?"

The above photo shows the hate mail Charlene Sumlin says her husband, Kevin, received this week. Twitter/@courshel

The letter contained a return address that corresponds to Houston Country Club, in Houston.

One of Sumlin's daughters, Shelby -- a current student at Texas A&M -- later commented on the photo, tweeting: "Imagine being a kid & reading this bs abt your dad. Things 'fans' say gets taken personal by more than just the coach. Humanity isn't hard."

Kevin Sumlin has faced heavy criticism since Texas A&M's season-opening loss Sunday at UCLA, in which the Aggies blew a 34-point, third-quarter lead. Texas A&M regent Tony Buzbee called for Sumlin's immediate dismissal in a Facebook post he published shortly after the game.

On Tuesday, Sumlin acknowledged the frustration both within and outside the program, but added, "I'm not in the business of really paying attention to anything outside this program, or comments good or bad. My focus is on what we can do to be better. I don't really have time to get involved in things that are said about the program or about me."

In a statement released Thursday night, after Charlene Sumlin's post, Texas A&M president Michael Young and athletic director Scott Woodward acknowledged the "disgusting and threatening letter."

"There is no excuse for hatred and, as a community, we will not allow the ignorance of some to intimidate any member of our community," the statement read. "On behalf of all Aggies, our thoughts are with Coach Sumlin and his family, and we will do all that we can to ensure their safety. We are working with law enforcement authorities to bring the sender of this letter to justice. We stand with the Sumlins and will not accept this inexcusable act of hate."

SEC commissioner Greg Sankey added on Twitter: "I have great admiration for Kevin Sumlin & fully support statement by Pres. Young & Scott Woodward. Letter sent to Sumlin home is sickening."

The Brazos County (Texas) Sheriff's office confirmed to ESPN that it has an open investigation into what happened.

Sumlin is one of seven African-American head coaches in a Power 5 conference.