you can also try this trick:
ps aux | grep puma
sample output:
myname 77921 0.0 0.0 2433828 1972 s000 R+ 11:17AM 0:00.00 grep puma
myname 67661 0.0 2.3 2680504 191204 s002 S+ 11:00AM 0:18.38 puma 3.11.2 (tcp://localhost:3000) [my_proj]
then:
kill -9 67661