Published: July 13, 2007 04:37 pm      

SATURDAY: How investigators track down the weapons used in street crimes (11:31 a.m.)

NEW YORK (AP) - The shell casings had barely cooled on a Brooklyn street when federal agents began trying to unwrap a mystery: How did three pistols get in the hands of the men who gunned down two police officers?

At the time, the agents had little to go on. The shooters were still on the loose.

Yet within hours, agents learned that the guns were originally sold by three shops in southern states. Powerful computer databases told them more. Two of the guns were several years old, meaning they had probably changed hands several times. Another was nearly new.

By the evening, the agents were headed south, hunting for prior owners of the weapons who might explain how the guns traveled north to New York from Virginia, Tennessee and Alabama.

In a way, this was routine work for one of the six regional gun-tracing centers run by the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Each day, the centers use a combination of science and shoe leather to track hundreds of firearms found at crime scenes, looking for clues that can lead investigators to a big break in a case, or put them on the trail of a gunrunner.

"Every gun has a story to tell," said William G. McMahon, the special agent in charge of the ATF's New York field office.

The good news is that telling that story has been getting a little easier.

Years ago, investigators trying to learn where a weapon came from had to browse file cabinets filled with index cards.

These days, investigators at ATF centers in New York, Miami, Chicago, Seattle, Los Angeles and Washington, D.C. have high-tech tools at their disposal.

Every sale of a new firearm at a licensed gun shop is recorded, and the sales data can be analyzed by computer for clues and trends.

Investigators also map where guns are recovered, sometimes with intriguing results.

The ATF's regional gun center in Chicago analyzed records related to guns recently seized from gang members and discovered that more than 300 of the weapons had been purchased from just four shops in Mississippi.

That lead resulted in the February arrests of 19 people on charges that they were buying weapons in bulk in Mississippi and illegally selling them to gang members up north.

"The hardware we have is top notch. The software continues to improve, and our analysts are great," said Andrew Traver, special agent in charge of the ATF's Chicago field division.

High tech isn't a cure-all, he said. But it helps agents stay on top of a mountain of guns. Last year, he said, Chicago police requested trace information on nearly 13,000 firearms.

"When you get down to it, the problem itself is almost overwhelming because of the volume," Traver said.

The task is made harder by limited manpower. Even the largest of the tracing centers has only a few dozen agents, plus a few officers detailed from city police departments.

That means investigators need to be somewhat selective in which crimes get their full attention, said Kelvin Crenshaw, the special agent in charge of the Seattle field division.

The speed at which the agents can work, however, was apparent Monday after NYPD officers Russel Timoshenko and Herman Yan were wounded after pulling over a stolen car.

The shooting happened at 2:30 a.m. The guns were found a short time later.

By 10 a.m. the serial numbers of the weapons had been delivered to the ATF's tracing center in Brooklyn, and by 1 p.m., investigators knew who first purchased the guns and where.

The next part of performing the trace has been harder.

Federal law doesn't require gun owners to register their weapons or report secondhand sales, so agents must rely on old-fashioned police work. In most cases, that means finding the original owners and getting them to talk about what happened to the guns after they bought them.

Tracking those people consumes a ton of manpower, "and a lot of times, it doesn't lead anywhere," said McMahon.

One of the guns used in the New York police shooting had at least three owners, including one now out of the country on a cruise. The agents reached him aboard the ship by telephone.

Another original owner had died years ago. The third gun had at least two previous owners. One is in prison.

ATF spokesman Joseph Green said investigators have yet to gather evidence to prove how the guns were delivered to the men now charged with the shootings.

The stakes are high. Timoshenko was still fighting for his life Friday.

And ballistics tests offered an additional surprise: The .45-caliber pistol used to shoot the officer was also used in an earlier drive-by shooting.

"We're going to keep at it," Green said. "Once you're on the trail, you never know where it may take you."