it was a mistake
No fue un error de Tom.
It wasn't Tom's fault.
It was a typo.
This was a mistake.
It was an unforgivable mistake.
Tomás sabe que lo que hizo fue un error.
Tomás knows that what he did was a mistake.
Dile a Tom que fue un error.
Tell Tom it was a mistake.
It was a very serious mistake.
Lo de las prostitutas fue un error.
The thing about the prostitutes was a mistake.
— Love Actually (2003)