I would go to government entities, county sheriff offices, etc. he's interested in, for example, here's the NC government:

http://www.doa.state.nc.us/yaio/interns.aspx

and see who has them; it may be a bit late to apply; the ones above had to be in by the beginning of December, last year.

The FBI is not doing them this year: https://www.fbijobs.gov/2.asp

State Department: http://careers.state.gov/students

If you have friends or neighbors in those fields, now would be a good time for your son to talk to them, see if they can find out more about where they work and internships.