Sheriff Bryant said the motive for the killings was unclear, but noted "it's my understanding that the suspect may have been suffering from some type of mental illness from being in the military himself".
Some federal sources said it was even too early to say investigators had identified the suspect, but several sources in Boston told CNN that they have a clear identification.
But the Chinese firm will be hard put to run Slavneft without local cooperation which makes some observers suspectit is really only in the auction to bid up the price.
"We highly suspect that it might be some form of acute poisoning from something that they had eaten, but we are still waiting for the laboratory results, " Nathan said.