How to track a phone number. ASAP!?

So my family has verizon wireless internet. When you pull up the app. to turn the internet on, there's this tab called TEXT MESSAGING. being nosy i clicked on it. One had the # and the message next to it said =Just to let everyone know, I put Jasmine to sleep this morning. She is buried out back. Spot & Roscoe were buried with her., another said like why are you running towards Sullivan Island. (FYI that's in South Carolina, we live in Louisiana) and no one has been there. So I wanted to know how you see who's phone number it is, but not by GPS. that won't help. Thanks!