In September 1998, Dr. William Birkin attempted to sell the G-virus to the US military, who were more than willing to accept the offer if it meant cutting ties with Umbrella in favour of developing their own, closely-monitored B.O.W.s.
Unfortunately, Umbrella's attempt to beat the military to the virus was a disaster - an infected Birkin exterminated the special team and released the t-Virus into the sewers, spreading the mutagen around the city. A special committee within Congress including Senator Ron Davis, approved the bombing of Raccoon City.
Cover-up and the search for 'the truth'
"I couldn't forgive them for covering up the Raccoon City atrocity. I refused to let the government rewrite the truth as they saw fit."
The US government refused to discuss their prior involvements with Umbrella, along with their foreknowledge of the t-Virus and the company's bio-weapons. This was controversial amongst conspiracy theorists who concluded that the only reason for the city to be destroyed was to suppress evidence linking them to the incident. It should also be noted that it would have been devastating for the government due to the Biological Weapons Convention, which it had itself signed.
In secret, this really was a conspiracy; the long-standing National Security Advisor, Derek C. Simmons, brought the Eradication Operation to the Congressional committee to manipulate them into deciding on the one action that would wipe away any incriminating evidence in the city - a thermobaric strike.
Because of the controversy surrounding popular theories, terrorists had been known to strike in the hopes of forcing the US government to reveal the truth regarding their involvement; Curtis Miller was radicalised by Frederic Downing with this thought. Not all bioterrorists felt the same way - Simmon's organization, "The Family", was against President Adam Benford's planned 2013 speech at Ivy University, where it was expected from inside-sources he would "go public" with the cover-up, resulting in the destabilization of world politics.