I'm not so sure you are at the level of being able to break your lease yet unless this happens to be a common occurrence and the landlord knows of the issue. Since the theft occurred in the parking area, I would first ask the landlord to provide a copy of his insurance policy to determine potential coverage for your damages. What you are faced with (on the damages aspect) is more in line with the services of an attorney that handles plaintiff's insurance work.
Again, I'm not trying to discourage you that you can't break your lease, but the better option might be to talk with your landlord about this first and if you are still not satisfied, you might need counsel. Don't just presume you can break your lease. This could lead to more serious issues with the landlord.