It wouldn't be the first time the US government kills its own citizens. Let's not forget about the unethical experimentation performed illegally and without consent on the test subjects.
"The experiments include: the exposure of people to chemical and biological weapons (including infection of people with deadly or debilitating diseases), human radiation experiments, injection of people with toxic and radioactive chemicals, surgical experiments, interrogation and torture experiments, tests involving mind-altering substances, and a wide variety of others. Many of these tests were performed on children,[1] the sick, and mentally disabled individuals, often under the guise of "medical treatment". In many of the studies, a large portion of the subjects were poor, racial minorities, or prisoners"
Wikipedia
And what about the involvement of the CIA on the crack cocaine epidemic that hit the African American neighborhoods?
We can go on and on about the American government and their greed... but I'll leave it at that
RE: 9/11 - Results From An Informal Steemit Survey -Does Steemit Believe The US Government Was Involved?