Chinese troops early on had German equipment, bought in the 30s. Seen pictures of chinese troops in German Stahlhelms and feldgrau wermacht-style uniforms.
ChiComs could have had them, after they ran the Nationalist troops out.
He could have captured it from some ChiCom “volunteer”, or taken it off his corpse. I’ve also seen vintage C-96 Broomhandle Mausers that were issued to the Chinese.
Anything’s possible, I suppose...
The other possibility is that it was his own personal weapon that he took along with him.
Where he got it from is the story.
Korea, Viet Nam and I think (not sure) even Iraq and Afgan troops could use personal weapons.