With that goal, the Magpies climbed above Bournemouth on goal difference. It came in the fifth minute of time added on, despite the fourth official having indicated there would be three.
Dean was again centre stage three minutes into the second half when he awarded Bournemouth a penalty as Federico Fernández wrestled Nathan Ake to the ground from a corner.
King sent Martin Dubravka the wrong way and scored his fifth goal in his last five home appearances.
From their next corner, Cherries centre half Chris Mepham almost put them in front as he looped a header inches wide of the far post from Fraser’s delivery.
Back came Newcastle and Matt Ritchie, returning to his former club, was a whisker away from putting Benítez’s side back in front as he got a toe to Rondón’s shot across goal but just missed the target.
An almighty goalmouth scramble then saw Bournemouth denied a goal by Paul Dummett’s acrobatic goal-line clearance after Callum Wilson looked to have nodded the ball over the line.
There was nothing between the teams with the game entering the final ten minutes but Bournemouth found a winner when substitute Dominic Solanke twisted and turned in the penalty area before teeing up King who finished first time into the left corner.