@Wolf359 said:

in the end the police squad stormed the house. but how v did they know that something is wrong?

Jodie Foster didn't blink or give him a signal at the door, right?

Probably years of experience had him sensing something was amiss. You could argue that she had a look on her face when they were asking her if all was okay before. She didn’t give a signal, but perhaps they were still able to sense something. I dunno.

@mechajutaro said:

That officer was the long lost brother of John Doe, in that proposed sequel to Seven which never came to pass. Dude had psychic powers, and read J. Foster's mind

Makes sense to me. He wanted to do something helpful, as his brother, John, was so screwed up.