Passed Base runner question

[TwoDot]

I had a strange event happen in LL majors game last night that I would like to find out the correct ruling.
With Runners on 2nd and 3rd, a past ball caused runners to try to advance. R3 got half way home, catcher ran her back to 3rd where R2 was standing on the base. R3 touches 3rd and then runs past the bag into the outfield. R2 then runs back to second, catcher throws to second base where R2 was tagged. R3 then runs home and scores.
The umpire (1st game ever) did not know what call to make R coach only wanted R2 to be out, run scoring. I did not think that was correct and we settled on R3 being out, and put R2 on third.
Somewhat unusual play that could only happen at this level, but I would like to know particulars as to what the correct ruling would be.