NEWSWEEK has learned that Colbern has admitted knowing McVeigh–but only as “Tim Turtle,” an alias McVeigh allegedly used to sell firearms and military surplus. The admission may help investigators trace McVeigh’s activities even if, as they now reportedly believe, Colbern had no direct involvement in the bombing itself. Already one of the biggest federal investigations in history, the OKBomb case now involves nearly 1,000 agents from the FBI and the Bureau of Alcohol, Tobacco and Firearms, plus hundreds of state and local cops across the West and Midwest. McVeigh, by all reports, is still not talking to the Feds. Meanwhile, prosecutors charged Terry Lynn Nichols, who had been held as a material witness, as a suspect in the crime. Nichols, McVeigh’s sidekick and former army buddy, was alleged in a 10-page government affidavit to have had a much larger role in the bombing than was previously believed-and according to government sources he has admitted helping drive the bomb truck to Oklahoma City on the day before the blast.

Like McVeigh, Nichols could face the death penalty if convicted on the new charges against him–and he seemed subdued and frightened during a brief hearing in a federal prison near Oklahoma City last week. The FBI’s affidavit lacked any broad theory of the bomb conspiracy’s members or motives. Instead, it recounted how McVeigh and Nichols allegedly met and acquired bomb ingredients and how the bomb was built, It listed evidence found in Nichols’s truck and in his home in Herington, Kans., including a receipt for ammonium nitrate fertilizer that supposedly bore McVeigh’s thumb-print. The most disturbing implication was also the most obvious -that Nichols and McVeigh had been working together since September 1994, six months before the explosion.

Newsweek’s reporting has produced new information about Terry Nichols. He subscribed to radical political theories espoused by a person identified with the Posse Comitatus, a violent, anti-Semitic right-wing group. And in November 1994, when Nichols flew to the Philippines for a reunion with his wife, Marife, he left an envelope with his first wife, Lana Padilla. It contained financial instructions, directions to a rental locker in Las Vegas that reportedly contained gold and silver bullion, and a letter to McVeigh. This letter, evidently written in case Nichols did not come back, said, “You’re on your own. Go for it!!” The letter apparently did not say what the goal was–though at another point Nichols wrote, “As far as heat, none that I know of.”

Meanwhile, the manhunt for John Doe No. 2 continued with no apparent sign of success. But Colbern’s capture could help, “The arrest of Colbern is part of a search for an associate of McVeigh who might help us clear up the mystery of John Doe No. 2,” a senior official said in Washington. “We are not saying he is John Doe No. 2.”

The emerging facts of Colbern’s background seemed to make him a likely fellow traveler with right-wing extremists like McVeigh and Terry Nichols. Colbern, 35, grew up in Oxnard, Calif., where he was known to high-school friends for his fascination with explosives. He graduated from UCLA at 29 with a B.S. in chemistry. He was married in 1986, went bankrupt in 1989 and was divorced in 1991. In 1993, he got a job as a research associate at Cedars/Sinai Medical Center in Los Angeles.

The weapons charge stems from a routine traffic stop in July 1994 in Upland, Calif. Police searched Colbern’s ear and found an assault rifle, a silencer and an “auto sear,” which is a machine part used to convert the assault rifle to full automatic fire. According to press reports, Colbern resisted arrest and was subdued by five officers. He was charged with possession of the auto sear and the silencer, which are illegal under federal law, but failed to appear for his trial on Oct, 21 The Marshal’s Service, noting that he was a survivalist, listed him as an armed and dangerous fugitive.

The Feds’ interest in Colbern grew exponentially in the wake of the Oklahoma bombing. Investigators learned that he had previously lived in a trailer park in Bullhead City, Ariz., which is about 20 miles from Oatman and 35 miles from Kingman. Kingman is the town where Tim McVeigh lived off and on from April 1998 to April 12 of this year. The area has long been a center of militia activity; according to federal sources, Colbern had ties to the right-wing underground there.

The fugitive stayed lost for months. Officials at Cedars/ Sinai said Colbern quit his job in November, and his father said last week that the family had not seen him since September. In January, Colbern showed up in Oatman and soon took a job at a local restaurant. He moved into a trailer owned by Preston Haney, a 52-year-old ex-marine. “He was radical–he didn’t like the government,” Haney told NEWSWEEK. Colbern’s employer at the restaurant, Lou Mauro, said Colbern took three weeks off in April to go back to California. But Haney said Colbern was in Oatman on the day of the bombing – and that Colbern said what happened to the children was “terrible.” While he may not be John Doe No. 2, the fugitive chemist may help the Feds trace the patriot under-ground–and find the key to the Oklahoma conspiracy.

With Colbern’s arrest–and charges against Terry Nichols–the Feds’ case widened last week.

McVeigh and Colbern in Kingman, Ariz., area; Colbern now says he knows McVeigh as “Tim Tuttle.”

Nichols joins McVeigh in a military-surplus business.

Colbern fails to appear to face gun charges.

Nichols buys 21 gallons of diesel fuel. Drives to Oklahoma City to pick up McVeigh.

A truck like Nichols’s is seen at a lake where Feds think the bomb was made.

Nichols turns himself in.

U.S. marshals arrest Colbern in Oatman, Ariz.