An English/American checkers man becomes a king when it reaches the farthest row. That promotion ends the turn, even during a capture. On a later turn a king can step or jump diagonally forward or backward. Kings do not fly over a row of empty squares.
Worked example
If a man jumps onto the king row, mark it K and pass the turn. Do not immediately turn around for another jump. The king's new backward-capture ability applies when it gets another turn, with the board as it then stands.
The Edge Changes the Turn
Red has a man on 22. White men are on 26 and 27. All other squares are empty. Red moves toward the top. Red must jump over 26 to the far row. Look at the remaining white piece, but remember that promotion has already ended red's turn.