If your ATM and/or credit card is missing, report them lost. Change any PINs immediately. Change any and all online passwords -- preferably to a combination of numbers, letters, symbols with no family birthdays or names or common words. If you have been hacked by a stranger, that's one thing; if someone you know has got access to your personal information, that's another.
Check with your bank and try to find out where the money went, when it went and if there is any record of the transaction. Did the person use the bank ATM? Are you sure it wasn't you? If there was a credit card purchase, track it down.
Protect your identity generally. Do not put personal identifying information on any bulletin board or social networking site; if it's there, delete it. No address, no phone number, no birthday, no kids' birthdays, no family names, no nicknames, no pet names. And don't use any of these as passwords.
Check out the FTC site for things you should do. Running a credit report is just the start.
DISCLAIMER: This answer does NOT constitute legal advice, create an attorney-client relationship, or constitute attorney advertising.
I've put in the link below my legal guide for victims of identity theft with tips on what to do to weed out the theft and protect yourself, so you won't suffer as much from this atrocity. Do not run a background check on yourself, but order your credit reports and file a police report, as my legal guide suggests. Such background checks may actually expose you to further identity theft and you must be particularly careful with who gets your personal information, especially online. There are many web sites and emails which spoof legitimate web sites and emails and get your personal information to steal from you. If I may be of any assistance, please contact me through my Avvo profile.