Immediately after suffering a wound (including a Shaken result from physical damage), your hero must make a Smarts roll or go Berserk.

While Berserk, his Parry is reduced by 2 but he adds +2 to all Fighting, Strength, melee damage rolls, and Toughness. The warrior ignores all wound modifiers while Berserk, but cannot use any skills, Edges, or maneuvers that require concentration, including Shooting and Taunt, but not Intimidation.

Berserkers attack with reckless abandon. Anytime his Fighting die is a 1 (regardless of his Wild Die), he hits a random adjacent target (not the original target). The attack may hit friend as well as foe. If there are no other adjacent targets, the blow simply misses.

The Berserker may end his rage by doing nothing (not even moving) for one full action and making a Smarts roll at -2.

Savage Worlds Deluxe Edition p. 35