Sure you have a claim - as long as you can identify and serve the two gunmen with a lawsuit. Otherwise, you don't tell us exactly who you think should pay. Compensation from who?
You may have a claim if there has been other violence at the restaurant where you were eating. For example if this is not the first time the restaurant has been robbed, you may have a negligent security claim. Contact the local police department and find out if there are other incidents at this location, or nearby. If so, contact an attorney.