In my state (NC) he could have been charged with assault by pointing a gun (ABPG), or communicating threats.
§ 14-34. Assaulting by pointing gun. If any person shall point any gun or pistol at any person, either in fun or otherwise, whether such gun or pistol be loaded or not loaded, he shall be guilty of a Class A1 misdemeanor. (1889, c. 527; Rev., s. 3622; C.S., s. 4216; 1969, c. 618, s. 2 1/2; 1993, c. 539, s. 17; 1994, Ex. Sess., c. 24, s. 14(c); 1995, c. 507, s. 19.5(d).)
§ 14-277.1. Communicating threats.
(a) A person is guilty of a Class 1 misdemeanor if without lawful authority:
(1) He willfully threatens to physically injure the person or that person's child, sibling, spouse, or dependent or willfully threatens to damage the property of another;
(2) The threat is communicated to the other person, orally, in writing, or by any other means;
(3) The threat is made in a manner and under circumstances which would cause a reasonable person to believe that the threat is likely to be carried out; and
(4) The person threatened believes that the threat will be carried out.
(b) A violation of this section is a Class 1 misdemeanor. (1973, c. 1286, s. 11; 1993, c. 539, s. 172; 1994, Ex. Sess., c. 24, s. 14(c); 1999-262, s. 2.)
I'm not sure if four guys coming at you is enough to justify threatening them. However, if he had taken the gun out, held it down, made no reference to it and did not verbally threaten the four, I feel they would have gotten the point and he would not have broken any laws.
I've done that on my own property - let the gun do the talking while I have it pointed at the ground beside my feet. Most people, even those that do not speak English, can understand firepower language that isn't even audible.