An individual is guilty of terroristic
threats if that person communicates- directly or indirectly- a threat to:
1) commit a violent crime with intent to frighten another;
2) cause a building or public transportation evacuation;
3) otherwise cause terror that creates a major public inconvenience.
The term "communicate" here means the threats would be conveyed by way of written or electronic means (telephone, e-mail, Internet, fax, telex, etc.)
A former roommate of mine had her boyfriend (at the time) put in jail for terroristic threats- among other charges. He had been screaming outside our apartment one night, when she wouldn't unlock the door, warning her that he would "cut her up" when she went to her car one day.