slump down
[for someone] to collapse and fall down; [for someone] to crumple. The shot hit Max and he slumped down. Suddenly, Mr. Wilson slumped down in pain.
slump down in(to) something
[for someone] to bend down or collapse into something, such as a chair or bed. Gary grabbed at his chest and slumped down into the bed. He slumped down into the chair and draped himself over the arm.
slump over
[for someone] to collapse and fall over forward in a sitting position. Just after the gunshot, Bruno slumped over and slid from his chair.