Sorry for your trouble, but that really isn't enough information for a diagnosis. There are a few things you can check, though.
On a 2.7 Charger, the most likely problem is a coolant leak. The first thing you (or he) should do is check the oil for signs of coolant contamination. If the oil is the color of chocolate milk, coolant has mixed with the oil and you probably have severe engine damage. If the oil looks like oil, you can check the coolant reservoir to see if it is full and looks like it should.
The next thing you should try is the
key dance. Make a note of any diagnostic trouble codes that you get and post them here.
There's a possibility that it's just a bad battery, or a loose or corroded connection. It's a good idea to check the battery terminals to see if they're clean and tight, and then check the grounds under the hood (they're close to the red cover that fits over the positive terminal for charging or jump-starting the car, and there are a couple of ground cables that connect directly to the engine block. Not sure exactly where they are on a 2.7.).
That's about all I can think of that you can do by the side of the road without much in the way of tools or resources.
