I had something similar happen with Wells Fargo. Logged in and saw someone else's name, Florida purchases (I'm in Montana), along with a different account number, statement history, etc.

Naturally, I recorded this with Quicktime and then called WF. Their response: "It's not a big deal -- neither accounts can withdraw money." After repeatedly explaining how serious this is for identity theft, I was told to wait 10 days. Their solution was to shutdown my online account without notice. If no one can login, then it's safe!

It took over a month to get this resolved, and once I could download my statements, I "cancelled" my account. WF is like Hotel California though -- a year and many phone calls later, my accounts still aren't closed.