Legal Question in Intellectual Property in Indiana

You would own the copyright if you were not not an employee of the website and the pictures were not specially commissioned and there was no written agreement. Distributing or selling those is not just a matter between you and the website. There are the rights of the artists at the concert and the concert regulations that must be reviewed to determine if there are trademark issues, privacy rights, etc. that would pose liability. You need to find a local copyright or entertainment law attorney in the state where the concert took place who is familiar with the local laws on such things. My educated guess is that you will find you can sell and redistribute these, but you must realize that doing so may be the death of your relationship with the company running the website. If that doesn't bother you then you should see the copyright lawyer as recommended and get clearance from the artists' agents (realize they may be your best customer if they like the pictures and you give them some sort of exclusive on the pictures, that is exclusive except for the website), otherwise talk with the website and see if they have a problem with them.