U.S. Sen. Lindsey Graham said he will propose legislation to prevent a repeat of an incident last week in which a Lady's Island woman, who once pleaded not guilty by reason of insanity, passed a background check and legally purchased a gun.

Days later, Alice Boland pointed the gun at an administrator and teacher at Ashley Hall, a private school in Charleston, S.C., and pulled the trigger, according to police reports.

Boland has been charged with attempted murder and four other gun-related violations. However, officials from the Charleston Police Department and U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives said she will not face an additional charge of illegally buying the gun, even though she filled out a required federal questionnaire that asks if the purchaser has ever been judged mentally deficient or committed to a mental institution.

"To me this is Exhibit A of a broken system," Graham said in a press conference Wednesday. "How can it be that the background check would allow her to buy a gun? How could it be that someone in the United States who pleads not guilty by reason of insanity is able to pass a background check and buy a gun?

"And thank God the gun didn't go off."

The magazine in Boland's .22-caliber semiautomatic Taurus was loaded with eight rounds, but it did not fire because there was no round in the chamber, according to Charleston police.

Graham said he is calling on other members of Congress to help him "fix the system" so others with mental-health problems cannot purchase firearms.

In 2005, Boland was indicted after she was accused of threatening to kill President George W. Bush, but the charges were dropped in 2009 after she pleaded not guilty by reason of insanity.

Graham, who was short on details of how to limit firearm access to certain people with mental illnesses, said a plan by Democrats to require more background checks won't work because a background check allowed Boland -- and presumably people with similar histories -- to purchase a gun.

It's not clear whether the law already prohibits those like Boland, who have a history of mental illness, from purchasing guns. The 1968 Gun Control Act prohibits gun sales to anyone who "has been adjudicated as a mental defective or has been committed to any mental institution."

Graham said his understanding is that Boland purchased the gun legally, and the Walterboro gun store that sold it to her on Feb. 1 did not break any laws.

"Our investigation has revealed there was no misconduct or illegal activity in the purchase and transfer of the firearm from the licensed dealer," Charlotte-based ATF spokesman Earl Woodham said Friday.

Graham acknowledged distinctions between those with a mental illness that makes them violent and those who are ill but nonviolent. He also acknowledged he has not made up his mind on how the law should treat those who are nonviolent but mentally ill.

"We're working on the legislation," said Kevin Bishop, Graham's spokesman, adding that it would limit gun sales to those whom "a court of law has found to be a danger to themselves or to others, lacks mental capacity to manage their own affairs, incompetent to stand trial, involuntary outpatient care, etc."

Efforts are also under way on the state level to limit access.

S.C. Attorney General Alan Wilson, along with the State Law Enforcement Division, lawmakers and law-enforcement officials, is working on a state plan to limit firearm access to those with mental illness, according to attorney general spokesman Mark Powell.

A roll-out date for the plan has not been announced, Powell said Wednesday.