I don't agree (yet) with those who call this person a terrorist. In very broad definitions (see Sorcha), inflicting terror is the only defining feature for 'terrorism'. If you follow such a definition, he (I know it would be correct to add 'or she' but somehow I can't picture Peg's predictive description being far off the mark here) surely is a terrorist.

Most definitions I recollect require an aim (like overthrow of a government, induce the USA to stop supporting Israel,...) in the sense of making someone else change their ways in addition to an act inflicting terror to call the act terrorism. An aim I don't see yet in this series of murder.

Wolfgang