Pulling the weapon is questionable and a grey area to be decided by the court in this case. Possessing the weapon to pull in the first place however is a clear crime. So at minimum he is guilty of one crime, and potentialy more.
Does that qualify under the "using a firearm in the commission of a crime" type legislation? You know, the kind we quickly support picturing ourselves being tough on some guy robbing someone, and in reality making firearm defense more risky and impractical.
If I thought I was just gonna get beat up a little then no, I wouldn't pull.
This is something I do have mixed opinions on. This is because the human body is quite vulnerable. Possessing a firearm and being rendered dazed or stunned, or being knocked unconscious allows anything in your possession to be taken and used by the attacker. It is pretty common for thugs after beating someone up to go through thier pockets/ pat them down. Also if he was dazed or knocked unconscious and fell into the water, drowning is a very likely possibility. The guy showed a willingness to push his girlfriend out of the way, what makes you think he would allow anyone to aid him later, or attack someone else taking the attention away from the drowning man and keeping it on himself?
Many altercations start as a fight, someone pulls something out, picks something up, etc and it is not a simple "get beat up a little".
Here is a video of a big guy challenging another guy who picks up a piece of trash (brake rotor) from the ground and the big guy gets knocked unconscious. While unconscious he is killed.
http://www.liveleak.com/view?i=a3a774027a
It could have just as easily been a rock, a tool or item on a dock, or any number of items people are surrounded with, something pulled quickly from a waistband, or just a solid punch. One good hit and your ability to determine or guide the outcome of the event, is over. Your safety will then be at the discretion of the attacker, and witnesses.
Notice all the cars in the video driving by, obviously seeing as one pulls over and watches. Risk themselves and confront the guy? No.
Think it would be much different on most streets in America if you get knocked out? Probably not. Unless a witness stops them, how much damage done, or whether you die will be at the discretion of the attacker. You won't be able to judge the situation and progressively alter the level of force you feel is necessary.