In what circumstances will a defendant be found guilty of a criminal threat?

In People v. Fierro (2010) 180 Cal.App.4th 1342, a challenge to the sufficiency of the evidence supporting a criminal threat conviction was rejected where the defendant stood by the victim's car, displayed what appeared to be a gun, and threatened to kill the victim "'right now.'" (Id. at p. 1346.) The victim was "'scared to death during the whole ordeal.'" (Ibid.) In finding that the sustained fear element was proven, the appellate court reasoned the victim testified clearly that he was facing a gun, was scared for his safety, and that this mental state was not fleeting. This was sufficient to prove the element of sustained fear. (Id. at p. 1348.)