Leary Smith says her 38-year-old mentally ill grandson walked into the Cash America on Mansfield Road in Fort Worth and bought a gun.

"Mentally ill people don't need no weapon,” said Smith. This is the receipt showing that Gregory Lynn Willis bought a pistol for $162 on June 1.

His grandmother says he's been diagnosed with schizophrenia and can't believe he was sold a weapon. “I would hate for him to be standing over me with a gun,” said Smith.

Willis has been committed by the courts several times to mental institutions since the 1990s. He's been arrested for armed robbery, aggravated assault and in 2016 arrested for domestic violence.

A Tarrant County judge found him mentally incompetent and ordered treatment. It’s all in the court files. "If he had a gun, he might get mad at me and shoot me. You never know when he might flip,” said Smith.

According to former ATF Agent Tom Crowley, federal law prohibits Willis from having a firearm.

“Not if you have been adjudicated from a court or if you have been involuntarily committed, so if a court finds you incompetent and sends you to an institution you are prohibited from possessing or purchasing a firearm,” said Crowley.

WFAA asked Cash America how Willis was able to purchase a weapon?

They did not respond.

His grandmother says she asked and they told her he passed the FBI background check. But how did that happen?

Crowley says unless it’s entered into the database. There’s no way for gun dealers to know the person’s history. "That information unless it gets to the FBI there is no way for them to know and letting the gun dealer know to stop the sale,” said Crowley.

Leary Smith sold the gun back to the store and says she is keeping an eye out on her grandson to make sure he doesn't get his hands on another one.