As TimK pointed out, the situation could be but may not be a Seki but without a diagram to show to us, it's not easy for us to guess what happened.
Seki : no one die, everyone live
During the game
$$ | a b O X O .
$$ | X O O X O .
$$ | . X , X O .
$$ | X X X X O .
$$ | O O O O O .
$$ | . . . . . .
The corner is not settled yet, as both players can choose to:...
It is possible depending on previous turns that some variants of the Superko rule would allow black to win that fight. For example, if black played A3, white might not be allowed to capture at A5 if ...