撒野 means 'to behave boorishly or atrociously' — losing self-control and acting rudely or wildly in public. It's a separable verb-object compound (离合词): the object 野 can be split off with measure words, modifiers, or aspect markers (撒什么野, 撒了一通野). You usually use it to criticize someone's unacceptable behavior, often with a tone of disapproval or exasperation.