alarming

(verb) fill with apprehension or alarm; cause to be unpleasantly surprised. Synonyms: dismay, alarm, appal, appall, horrify. Examples: "I was horrified at the thought of being late for my interview." "The news of the executions horrified us."

(verb) warn or arouse to a sense of danger or call to a state of preparedness. Synonyms: alarm, alert. Examples: "The empty house alarmed him." "We alerted the new neighbors to the high rate of burglaries."

(adj) frightening because of an awareness of danger. Synonyms: alarming (vs. unalarming).