Federal investigators now have evidence linking the two principal suspects in the Oklahoma City bombing to the robbery of an Arkansas gun dealer last November and speculate that this may explain how the bombing was financed.
In what could quite literally be the key to the case, a bank safety deposit key stolen in the robbery of the gun dealer's home in November was found in April when federal agents searched the Herington, Kan., home of one of the bombing suspects, Terry L. Nichols.
And the robbery victim believes that Timothy J. McVeigh, the other principal bombing suspect, may have been involved in the robbery, in which a masked man knocked him unconscious, bound and gagged him, and took guns, jewels, gold and silver valued at almost $40,000.
The discovery of the stolen safety deposit key in the Nichols home and the possible connection between the bombing and the robbery were disclosed in an affidavit filed in U.S. District Court in Detroit on May 3 and unsealed Tuesday.
The financing of the bombing has puzzled investigators all along.
Although the bomb itself could have been built at little cost -- the materials, fertilizer and fuel oil, are estimated to cost about $3,000 -- Mr. McVeigh was often noticed paying cash for his expenses from a large roll of bills.
However, neither suspect seemed to have a ready source of money. Both scraped along on short-term jobs and a marginal business selling guns and military equipment at traveling gun shows and swap meets.
FBI agents trying to follow the money trail say they now believe the bombing was financed by robberies. In the past, they have speculated about a string of Midwest robberies committed by two or more men who used homemade bombs as a threat.
The affidavit was filed in support of an application to search the home of Mr. Nichols' brother, James D. Nichols, in Decker, Mich. That search was carried out, but investigators have not disclosed the results. And the detailed list of items seized from Terry Nichols' home has not been revealed.
If investigators can link Mr. McVeigh and Mr. Nichols to the Arkansas robbery, they would be able to tie them together in a criminal enterprise stretching back at least to last November, a period in which investigators so far have turned up a number of tantalizing leads.
The discovery of a possible connection between the bombing and the robbery could also mean that it was carried out, not by a large conspiracy, but by a much smaller group, these two and perhaps a few others.