One key element is the element of surprise. For example, in a 3 - line story where everything seems normal at first and then suddenly something terrifying happens. Like a person sitting alone in a library reading, all is quiet, then a whisper comes from the empty chair beside them. This unexpected turn makes the reader's heart skip a beat.
The element of surprise. For example, 'I sat on the park bench. The empty bench beside me whispered my name.' Just a simple, unexpected twist in the second line can be very effective.