Stop talking, ask for a lawyer, and do not consent to any further search. Anything you say about the gun, including "I didn't know it was there," becomes evidence about possession. Do not post about the arrest, do not contact anyone else involved, and do not try to move or dispose of any other firearms at home, which can be charged as obstruction or a bail violation. Write down what happened during the stop while it is fresh: why the officer said you were stopped, what was said before the search, who else was in the car, and where the gun was found. Bring every court paper you were given to your consultation. Your District Court arraignment will likely happen within a day, so calling a lawyer before that appearance gives you a chance to argue bail with real information instead of showing up unprepared.
