Getting a user that has deleted rows with SQL is a multi-part process.
First you have to search the transaction log file for information on deleted rows.
SELECT [Transaction ID], Operation, Context, AllocUnitName FROM fn_dblog(NULL, NULL) WHERE Operation = 'LOP_DELETE_ROWS' --Get Deleted Rows & Transaction ID
This will show you the Deleted Rows and give a Transaction ID for each operation. Now you need to use this Transaction ID to get the transaction SID of the user who has deleted the data:
SELECT [Transaction ID], Operation, Context, AllocUnitName FROM fn_dblog(NULL, NULL) WHERE [Transaction ID] = '0000:0000035' --Example Transaction ID to Delete AND Operation = 'LOP_BEGIN_XACT' --GET Transaction SID
Finally, you need to convert the Transaction SID into readable text to display the user details:
SELECT SUSER_SNAME(0x0105000000000002120000009F11CA398C81F81398D0CD14E8030030) --Based on Transaction SID That Was Returned Earlier