At first, Sean didn't plan on revealing his discovery.
If the police could find the clues, Sean would be happy to hide his true abilities.
Exposing one's abilities to the police is not a wise thing to do.
However, Mark had hidden the clues very well. The policemen saw Mark's wife and daughter at home, looking pitiful, so they were more "polite" and restrained in their search, which didn't turn up anything useful.
Sean had no choice but to speak up and remind them.
Upon hearing Sean's words, Paul Walker rejoiced and immediately prepared to go upstairs.
Mark's wife's face changed drastically!
She was not as innocent as she seemed!
She knew about most of Mark's activities!
After all, her husband's money was what she lived off of, and she didn't have a job herself. How could she not know what her husband was doing?
So she was well aware that his activities were illegal.
However, her husband was very discreet in his activities, so she wasn't too worried.