Simple past tense and past participle of alert.(verb)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "alerted" in a sentence
"Sarah Palin alerted people because she saw what they wanted to do to people like her son Trig, who the leftist radicals believe should of never been born (right now in this country close to 90% of Down Syndrome babies are aborted)."
"Dorothy Martin alerted them first to the space-landers coming to retrieve them from the flood."
"Our friend and frequent voice here on FlyTalk, Joey Lin alerted us to this video one of his clients shot the other day on the rio Corrientes in northern Argentina."