Personally, I think it should be assassinated by someone from Tricell company, no matter what the reason. Finally, it was Tricell, a new pharmaceutical company in resident evil 5, who cleaned up the wreckage for Wilpharma. It is quite possible that Wilfama was controlled by Tressel. After Wilfama's research center in Haverville was destroyed, Tressel came out to clean up the mess. The senator was silent because he owned shares in Weill Pharmaceutical and knew too much inside information. Naturally, there were some hidden information in the computer, so it was deleted. Because Frederick's G virus was obtained on the black market, the number will certainly not be much. In addition, it is impossible for many G viruses to flow from raccoon city to the black market, but the virus was injected by hairy men, so General Gordon didn't get the G virus. In addition, Frederick was caught by Leon and Claire when he was preparing to abscond with T virus and antibodies to T virus, so General Gordon didn't even get the T virus.
The above is purely a personal test, and I look forward to the answer of the official story!