If not for an alert suburban sheriff with a keen memory for names and old murder cases, another mentally deranged killer with an arsenal of semiautomatic weapons might well have inflicted a bloody catastrophe on some unsuspecting Twin Cities school, shopping mall or movie theater.

Minnesotans should thank Carver County Sheriff Jim Olson for intercepting Christian Philip Oberender and his 13 guns before they could act out his chilling impulses.

"I am so homicide," the 32-year-old Oberender wrote last month in a disjointed letter to the mother he had murdered in 1995. "I think about killing all the time. The monster want out. He only been out one time and someone die."

Also found in Oberender's home on Jan. 2 -- the same Delano house in which he had killed his mother -- were notes about the school massacre in Newtown, Conn., and about how guns kill too quickly, without inflicting enough pain and suffering.

How someone like Oberender, who at 14 used a shotgun to ambush his mother and was judged criminally insane for it, could emerge a few years later, sail through state and federal background checks, obtain a gun permit, and "legally" assemble an arsenal that included an AK-47 assault rifle, a Tommy gun and a .50-caliber Desert Eagle pistol, is hard to explain.

Yet Oberender's case is one of dozens, perhaps hundreds in Minnesota that expose dangerous loopholes in federal gun laws and in the state's system for checking the criminal and mental-health histories of prospective gun buyers.

As outlined by reporters Paul McEnroe and Glenn Howatt in last Sunday's Star Tribune, it's hard not to conclude that current background checks are deeply flawed and that spotty, unreliable federal and state databases leave the police and the public woefully unprotected.

"It gives a false sense of security," said Hennepin County Sheriff Rich Stanek, who has emerged as a strong critic of Minnesota's (and the nation's) failure to effectively handle issues surrounding guns and mental health. "The mentally ill should never have access to guns."

According to the news story, Oberender got his permit to purchase guns last May by transposing his first and middle names and by lying about his mental-health history. When authorities checked his background on state and federal databases, his name, his juvenile murder conviction and his history of mental illness failed to pop up.

How could that be? Sloppy recordkeeping, inadequate funding, bureaucratic incompetence, foolish privacy laws and ideological opposition to gun control may all play a part in this and similar cases. That's unacceptable, because complete, reliable information is the best weapon against crime and the best safeguard for the public and police.

An officer deserves to know, by the click of a computer, what kind of suspect he's dealing with. To deny a police officer solid information is like pulling the pistol out of his holster. Yes, it's naive to think that some people who shouldn't have guns will not find a way to get them, but government shouldn't be sanctioning their purchases. It's hard to believe anyone could argue that people like Oberender should have the legal right to bear arms.

Legislators in Washington, D.C., and St. Paul must revisit, tighten and reinforce the background-check system. It's a sham that the FBI's national database is voluntary and thus contains only a tiny fraction of the states' criminal and mental-health records.

It's a disgrace that some law-enforcement officials, including at least one sheriff in Minnesota, refuse to fully enforce gun laws that protect police and citizens. It's imperative that Minnesota follow instead the lead of sheriffs Stanek, Olson and others to plug the dangerous holes in the state's background-check system. It's a matter of life and death.

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An editorial of the Star Tribune, Minneapolis.