Unfortunately, this is a difficult question to answer. It sounds as if this individual is not very stable and may have an underlying psychological condition (possibly bi-polar disorder). Individuals who have a psychological condition and are experiencing psychotic symptoms, are not taking their medication or are abusing drugs or alcohol have an increased capacity to harm themselves or others. If he fits this profile, the chances are higher he may act on his threats.

If it has already gotten to the point of being charged for his actions, I think your friend must take the threats seriously. She should probably takes steps to protect herself. Here are some ideas:

1. Never be alone. Until the threat subsides, always have someone around-at work, home and even in the car.
2. Notify employer of potential problem. They may be able to avoid a problem by not allowing him into the building, or calling the police if he is seen. This goes for neighbors as well.
3. Retraining Order- Can help escalate the issue legally if he continues making threats.
4. Self protection- Get pepper spray and think about taking a self defense course.
5. Talk to people who know him- confidentially. Consider talking to friends or family members who may be able to shed light on the situation. If they care about him, they are probably concerned as well. Perhaps individuals who are close to him could let her know if he gets worse, or seems unbalanced.
6. Change schedule- don't take the same route to work, alter meal times- try to be unpredictable- in case he is following her.
7. Move- If it is enough of a threat, it may be worthwhile to move to another part of town or in with a friend until the situation gets better.

I hope the guy calms down and it turns out he was just trying to get attention.

The only answer to this is how much of a nut is the person who made the threats. If you think he is serious than arm up. If he is just some BS then call him out to your advantage. Most people are full of it but there is the occasional nut out there. I find the more people talk the less likely they will act. People who are going to do something usually just do it.

I would go to that person prepared for a fight and give him the chance to make good on his threats and get it over with. why live in fear? you are responsible for your own safety. cops cant do anything meaningful till AFTER he kills you

I would never take such a threat lightly. To that end, your friend was wise to call the police and keep a record of what happens. Unfortunately, aside from being as safe as possible, and not provocative, there isn't a whole lot you can do.