Ok, here's my insight on the matter since I have dealt with many situations involving "brandishing" (it's in quotations because most people don't understand the concept, although most on this site do). 9-1-1 gets calls all the time with people calling in saying they got "robbed" when in reality they get their car was broken into the night before which is incorrect. There is a lot of conflicting statements made by citizens to the police. Trust me (or don't), the police understand that some complainants 1: don't know laws, 2: might not have a proper mental capacity/intelligence, 3: lie, 4. embellish. It's called investigating the matter fully to make sure the outcome is just and legal. If not, then the LEO/agency/state will be held liable (laws in place already for that).
If a complainant claims someone "brandished" a firearm, there are a few things that will occur. The officers will meet with the complainant and get their side of the story and hopefully meet with the "suspect" and get their side. Given most circumstances, the suspect will legally be stopped (terry stopped/detained) and disarmed during the duration of the investigation. The officers will need probable cause to make the warrantless arrest (misdemeanor brandishing exception was already mentioned above). Now, brandishing is a misdemeanor, and misdemeanors in VA are released on a summons. However, there are exceptions to releasing on a summons (criteria and/or crimes). Brandishing is easily articulated as one of those crimes. 19.2-74 states that you can make a custodial arrest for a misdemeanor (with probable cause and that falls into the legal requirements of an arrest) if you believe the person is a danger to others. So if someone just brandished a firearm, it's simple to reasonable state they are dangerous to another person and therefore you will be taken forthwith to jail/magistrate after making a custodial arrest. The gun is evidence and will legally be seized. If the investigation appears that the complainant was wrong and no crime was committed, the "suspect" will immediately be allowed to leave.
From personal experience, if both the suspect and complainant have very conflicting statements and officers are comfortable making an arrest... usually the officers will... 1: Detain the "suspect". 2. Take the complainant to the magistrates office to speak with a magistrate and swear out the warrant themselves. 3: If the magistrate issues a warrant, the officers will then arrest the "suspect". If not, the suspect will be immediately released, and the firearm returned. Remember, in VA, any citizen can petition a magistrate for a warrant, not just LEOs.
This is just my insight, I know I am disliked but I figured some still would find a LEOs POV interesting on the subject. I'm not saying I agree or disagree with how things work that I mentioned above, I am merely bringing it to light. Also keep in mind, there are many instances where people legitimately brandish guns at others in a threatening manner. At times, brandishing calls will evolve into situations where people (citizens or responding LEOs) are shot/killed.
Also, found this earlier, and thought you all might think it's interesting..
http://www.wpxi.com/news/27425029/detail.html