[racket-dev] Help with build failed error message

I made a fork of the racket repo and committed some changes in a topic branch, but I got this:
make[8]: Leaving directory `/home/travis/build/AlexKnauth/racket/racket/src/build'
make[7]: Leaving directory `/home/travis/build/AlexKnauth/racket/racket/src/build'
make[6]: Leaving directory `/home/travis/build/AlexKnauth/racket/racket/src/build'
racket/racket3m -X "/home/travis/build/AlexKnauth/racket/racket/collects" -G "/home/travis/build/AlexKnauth/racket/racket/etc" -G /home/travis/build/AlexKnauth/racket/build/config -N "raco" -l- setup  --no-user -j 2  
raco setup: bootstrapping from source...
Killed
make[5]: *** [install-3m] Error 137
make[5]: Leaving directory `/home/travis/build/AlexKnauth/racket/racket/src/build'
make[4]: *** [install] Error 2
make[4]: Leaving directory `/home/travis/build/AlexKnauth/racket/racket/src/build'
make[3]: *** [base] Error 2
make[3]: Leaving directory `/home/travis/build/AlexKnauth/racket'
make[2]: *** [plain-in-place] Error 2
make[2]: Leaving directory `/home/travis/build/AlexKnauth/racket'
make[1]: *** [cpus-in-place] Error 2
make[1]: Leaving directory `/home/travis/build/AlexKnauth/racket'
make: *** [in-place] Error 2
The command "make CPUS="2" PKGS="racket-test db-test unstable-flonum-lib net-test"" exited with 2.
(lines 812-830 of https://travis-ci.org/AlexKnauth/racket/jobs/30368892)

What does this mean?

What does the “Killed” mean?
And what is error 137?

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