Sounds like identity theft to me.  File the paper return ASAP, and tell him waiting until May is not as safe as filing in February before someone who knows his name and SSN decides to use them. 

IRS says it is working on Forms 14039 (Identity Theft Affidavit) filed in October 2023.  And that was before 50% staff reductions.  He'll earn 8% interest on the refund, though!  (Eventually.)