We've killed the wrong one: Run script not aborted properly

On my local Debian Jessie machine, run.sh kills the wrong process.

This is the output of ps -ef | grep runserver.

nico      7961     1  0 20:54 pts/1    00:00:01 python3 manage.py runserver
nico      9061  7961  3 21:05 pts/1    00:00:03 /usr/bin/python3 manage.py runserver

This shutdowns the server: pkill -P 7961.

This does not: pkill -P 9061.