"Once again, we have tragically proven that we are failing to be responsible for the rights our freedoms grant us," the Oscar-winning actor, 52, wrote in a statement posted to social media.
"The true call to action now is for every American to take a longer and deeper look in the mirror, and ask ourselves, 'What is it that we truly value? How do we repair the problem? What small sacrifices can we individually take today to preserve a healthier and safer nation, state and neighborhood tomorrow?'" the Dallas Buyers Club star, who spent his early childhood in Uvalde, asked. "We cannot exhale once again, make excuses, and accept these tragic realities as the status quo."
The father of three called on all Americans to "re-evaluate, and renegotiate our wants from our needs. We have to rearrange our values and find a common ground above this devastating American reality that has tragically become our children's issue."
McConaughey called the mass shooting — on the heels of another one at a Buffalo, N.Y., grocery store last week — "an epidemic we can control, and whichever side of the aisle we may stand on, we all know we can do better. We must do better. Action must be taken so that no parent has to experience what the parents in Uvalde and the others before them have endured."
He ended by writing, "To those who dropped their loved ones off to school not knowing that today was goodbye, no words can comprehend or heal your loss, but if prayers can provide comfort, we will keep them coming."
McConaughey was born in Uvalde, which is about 85 miles west of San Antonio, in 1969. His mom, Kay, was a teacher and his late dad, Jim, was in the oil pipe supply business. In 1980, McConaughey's family moved to Longview, where he graduated high school before going on to college at UT-Austin. The actor still resides in Austin today along with his wife, Camila Alves, their children (Levi, 13, Vida, 12 and Livingston, 9) and his 90-year-old mother.
Last year, McConaughey considered a run for governor, against incumbent Gov. Greg Abbott, a Republican, but announced in November that he decided against it. At the time, he said, "As a simple kid born in the little town of Uvalde, Texas, it never occurred to me that I would one day be considered for political leadership. It is a humbling and inspiring path to ponder. It is also a path that I'm choosing not to take at this moment."
On Tuesday, an 18-year-old gunman fatally shot 19 children and two teachers at Robb Elementary School in Uvalde before he was killed by law enforcement. Prior to being at the school, the shooter also shot his grandmother.