You can try 3rd party tools available in the market, which will allow you to recover your deleted records from sql server database file.
I can suggest you a sql recovery tool from http://www.systoolsgroup.com/sql-recovery.html
For further drilling down to know who deleted and who modified the database records, you need to take help of SQL Server log files. Logs files are stored in same folder as of master.mdf and having file extension as .ldf. Get a sql server log file reader to view logs and see who deleted and at what time.
Other tool to view sql server log files to view sql server database operations like modifying, deleting or adding can be downloaded from http://www.systoolsgroup.com/sql-log-analyzer.html