Our local media finds a local person injured out in the CA car racing wreck:
This seems to happen all the time - our local media somehow finds out a local person is involved in a national news event. I assume that it happens in other media markets too.
Do these people contact local media? Or maybe their relatives contact the media?
I imagine the media may be directly contacted by the individuals at times who may be seeking their 15 minutes of fame. Investigative reporters will also speak with witnesses to obtain contact info of victims. When you have an unusual incident such as this the media wants to adhere to the ritual of, “If it bleeds, it leads.”
Longtime reporter here. Most of the time we get “the local connection” from other people in the community who bring the person to our attention. Often a relative, sometimes a neighbor, usually not the person themselves. We have a variety of tools at our disposal to get people’s contact info… that’s the easy part.
And a nitpick to what Dereknocue67 said. Investigative reporters are those who do broad investigations, such as looking into government corruption. A beat reporter would cover a story like this.
…they have to be beat to get them to write the story? Rough business, we’re not even allowed to lightly slap employees. 
No, they just have to beat them until they sober up enough to go ask the questions. They usually stay sober enough to actually write the story on their own.
As soon as CNN shows something that involve one or more persons, the newsroom scrambles to find out if there any “area men” involved. I used to do in in the pre-internet days. It was rough. Dozens of phone calls all over … various police departments, etc. Usually, we’d come up empty-handed until, as Anson says, someone called in to say, “I’m his mom.”
It turns out I just found out an example of this today. A guy I work with has a son on America’s Got Talent now. He posted local articles about his son. He told me he contacted the local media about his son and they ran the stories.
I used to keep a copy of the Dacron, Ohio Republican-Democrat (“one of America’s newspapers”) on my coffee table.
Front page news: Japan Destroyed! Local Ladies Feared Missing [pic of ladies].