Act as though you were in church or a synagogue, unless your church calls for loud singing and spontaneous "hallelujiahs". Dress as though you were going to a job interview. (No marijuana leaves on the front of your shirt or anti police slogans). Be respectful and NEVER make a scene, by rolling your eyes, dropping your head into your hands or talking excitedly to your attorney.
Retain an experienced criminal defense attorney in your area to assist you who also understands the immigration consequences involved since certain dispositions will result in you not having a criminal recors yet still effect your immigration status. There are many excellent attorneys here on AVVO and most offer free consultations.
The decision whether to prosecute or not prosecute a case is made by the prosecutor's office. Your brother can certainly contact that office and indicate that he does not want you to be prosecuted, but he is not empowered to "drop" any charges.
The Second Amendment was drafted immediately following a revolution that resulted in the United States of America. The historical context is that we did fight a government we felt was "tyrannical". However, that was more than 200 years ago when the principal weapon employed by soldiers was a musket. In 2013, do you really think a 9mm Glock, or an AR-15 Bushmaster or even an AK-47 will do anything in a "revolution against tyranny" against a government supported by Abram tanks, Stealth fighters...
You should consult with an experienced personal injury attorney as soon as possible, There are many fine ones here on AVVO. Do you have medical insurance? If so, go get whatever treatment you require. If not, you really need to hire an attorney. Good luck.