All the FBI and ATF Agents were out of the building, however, there were some ATF admin personel in the building.
"Luke Franey (a BATF agent who claimed he was in the building) was not in the building at the time of the blast, I know this for a fact, I saw him! I also saw full riot gear worn with rifles in hand, why? Don't make the mistake as I did and ask the wrong people."
From a letter by the first OKCOD officer in the building after the explosion,Terry Yeakey, before his murder.