I didn't give poor advice, I specifically told her to go ahead and contact the authorities to have them run a background check on the guy. As for baiting him into implicating himself in a way that can be proven (hard trail evidence), that's the only way you're ever going to get the authorities to act. Even with that, they may not do anything.
I think its much better to gather that evidence where you're one step ahead rather than one step behind. If he is 'disturbed' in some way and has targeted Chandrika, he'll just find some other avenue now, regardless of the whole internet thing. Better to set a trap for him rather than wait 'til something terrible happens. Aside from a possible background check, unless you have some clout downtown you'll be hard pressed to get any action from the authorities without hard proof, or until after the fact.
If you don't believe me just call up your local district attorney and get their response, whether they'd do anything based on undocumented (verbal) threats or mere suspicion... good luck. Depending on the circumstances and who's involved, don't be surprised if they say they can't do anything 'til it gets bloody... and even then there's no guarantee depending on how serious it is, and especially, not without proof.
Perhaps a home surveillance system might be in order, that or ask the apartment complex (assuming its an apartment complex) about installing a surveillance system on the premises somewhere.