Accused gunman Jared Lee Loughner faces five criminal charges after he allegedly shot dead six people and injured 14 in Saturday’s Tucson rampage. But the 22-year-old will not face charges on at least one count: law enforcement officials say Loughner legally obtained the Glock 19 pistol used in the shooting from a licensed dealer.

So how did Loughner, an apparently unstable person, get a gun?

Experts point to several answers.

According to Loughner’s former teachers and classmates quoted in news reports, the community college drop-out would often behave bizarrely in class and appeared to be mentally disturbed. He also posted rambling YouTube videos in which he discussed government mind-control tactics.

In October, Pima Community College President Sylvia Lee suspended Loughner and required he undergo a mental examination to determine whether he was a danger to himself or others before he could be readmitted, Lee told CNN. He never underwent examination. Instead, he dropped out of school. With no mental health records on file, Loughner could not be considered “unstable” by Arizona and was able to legally purchase a gun.

Some experts caution that government collection of individual psychiatric records could infringe upon fourth and second amendment rights.

Dr. Victor Schwartz, associate professor of clinical psychiatry at the Albert Einstein College of Medicine of Yeshiva University said, “Odd behavior in a college class shouldn’t cancel someone out for having basic civil rights.”

“You can’t show records that prove you’re not mentally impaired,” said Bob Levy, a constitutional lawyer and chairman of the board at the libertarian Cato Institute. “It would be intrusive to require permission from a licensed psychologist.”

Uneven state and federal oversight may have also played a role, according to gun control advocates.

Arizona bars applicants who have suffered from mental illness, been “adjudicated mentally incompetent” or been committed to a mental institution from obtaining a permit. Similar laws exist in Tennessee, New York and Virginia. But fewer than half the states conduct some type of mental health background check on gun permit applicants

The Federal Gun Control Act of 1968 bans the sale of guns or ammunition to anyone who has been found to be a danger to himself or others; the 1993 amendment to that law, known as the Brady Bill, requires federal background checks of handgun purchasers.

After the Virginia Tech shooting in 2007, Rep. Carolyn McCarthy introduced the NICS Improvement Act of 2007. This amended the Brady Bill to require federal agencies to collect records relevant to applicants’ mental health statuses.

Arizona has trailed other states in reporting applicants’ mental health information to the federal government. Since Rep. McCarthy’s bill passed, states have sent more than 930,000 mental health records to the National Instant Criminal Background Check System. But statistics compiled by the Brady Campaign to Prevent Gun Violence found that Arizona submitted mental health data only 4,465 out of 121,700 records it sent to the federal government.

“No federal laws were broken in purchasing the magazine or the firearm,” said Brian Darling, the director of government relations at the Heritage Foundation, a conservative think-tank in Washington.  “Maybe Arizona just didn’t follow through with what it should have.”

Loughner’s actions also raise questions as to whether there are enough resources to adequately treat the mentally ill. Forensic clinical psychologist and professor at the University of Virginia Dewey Cornell said that lawmakers need to offer affordable clinics for people even suspected to be mentally ill to prevent them from obtaining firearms.

“It would be more cost-effective to take a preventive approach than wait for a mentally ill person to commit a crime,” Cornell said. “That’s what’s happened in this country: the criminalization of the mentally ill.”

He added that some lawmakers are hesitant to fund psychiatric facilities in a recession. Without proper treatment, the mentally ill are three times more likely to be violent than average people, according to the National Institute of Mental Health’s statement on the shooting. More mental health resources (ranging from counseling to education), along with more state and federal reviews of applicant records, could prevent another massacre, Cornell said.

On behalf of the National Rifle Association, media liaison Alexa Fritts issued this statement: “At this time, anything other than prayers for the victims and their families would be inappropriate.”