[Idiom] turn sb in the second

[Llandeilo]

Waht does this idiom mean?
Example (from 'Hunger Games' vol 2, p 220)
quote:
'I tracked down Ripper this morning and told her I'd turn her in the second she sold [liquor] to either of you.'
unquote

 

[Tdol]

Report her to the police or authorities.

 

[emsr2d2]

I told her I would turn her in.
When would you turn her in?
The second she sold liquor to either of you.

"The second" means "immediately" or "at the exact instant".