Car is going bonkers.

So we couldn't unlock the door with the key.  
Locksmith had to come unlock it.
Now there's only one key hole to open this van
which is on the driver's door.  
Locksmith said the alarm is going to keep going
off that we should just cut it but he didn't know
where the cord would be.
So we can't even lock the doors anymore either or
else we're out of luck.  
Now my question is how do we fix this problem.  
And what is the exact problem.
The locksmith thinks the driver door look for the
key is broken.
But he's not sure.
Even though the key still turns on the car.
I need help please?