Federal agents are tracing the history of the weapon used in the fatal shooting at Reynolds High School.

Six agents from the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives responded to a request for help from Troutdale police. Among the tasks they are undertaking is an "urgent trace" on the gun. When they are done, agents could ultimately know the name of every person who owned the rifle used to kill one student and injure a teacher.

Last year, the ATF traced 3,600 guns in Oregon, including 947 rifles. The agency also traced 35 derringers and 15 machine guns. Nationwide, ATF traced 336,000 guns connected to crimes, according to a report released Monday.

Oregon guns

Provides details on information gathered in tracing guns in Oregon in 2013.

Pro Publica, a national investigative reporting organization, produced this view of data from ATF’s 2012 gun checks.

ATF maintains no database of gun owners. Instead, each gun has to be traced from scratch, which can turn into a laborious process.

The process starts with a local police request to ATF's National Tracing Center in Virginia. The center first contacts the gun manufacturer, learning to which wholesaler the gun was sold. The wholesaler, in turn, will lead agents to the local retailer.

ATF Special Agent Brian Bennett, public information officer for ATF's division office in Seattle, said retailers are required to keep records of each gun sale, including their background checks done before sales are completed.

"We will try our best to find that original purchaser," Bennett said. He said agents follow leads to contact every known buyer of a gun. With private sales, there often are no records, making tracing a challenge, Bennett said.

Bennett said agents will work around the clock to build that gun history in instances such as the Reynolds shooting.

He said the weapon usually is swabbed for DNA samples and checked for fingerprints. Bennett said even when a suspected shooter is dead, agents still work to build the gun's history.

"The gun is another part of the evidentiary puzzle," Bennett said.

Such tracing can help investigators pin down how a suspect got a gun and determine whether there are accomplices.

Not every trace requested by law enforcement produces such a thorough reconstruction, Bennett said. In most normal requests, the National Tracing Center can get the information it needs with a few phone calls.

ATF's 2013 tracing report showed Oregon guns were traced as "found weapons" in 692 instances. The agency also traced 669 instances of "possession of firearms," involving guns recovered by police from individuals. Among other reasons guns were traced were 162 instances of suicide.

The agency tracks from what state a gun originated before it ended up in Oregon. Last year, Washington was the source for 159 guns, with California next at 133. The cities with the most weapons traced by the ATF included Portland (815), Eugene (310), Grants Pass (255), Medford (233) and Salem (191).

-- Les Zaitz