Batch commit did not work
Difficult to diagnose definitively based on the information provided but the likely cause is the batch was inadvertently invoked with a transaction already open. I suggest one or more the following to prevent the problem going forward:


Add SET XACT_ABORT ON; to the batch to help ensure explicit
transactions are automatically rolled back.
Remove the superfluous BEGIN TRAN and COMMIT since the automatic
single-statement transaction will fully rollback a delete batch if an error
occurs.
Add error handling