Cassandra pod killed frequently

[tharpa]

I deploy Cassandra to a k8s cluster using your Cassandra-kubernetes service and replication controller definitions. Unfortunately, the Cassandra pod is restarting frequently and these are the last lines from the pod log:

INFO  15:25:25 Cassandra version: 3.5
INFO  15:25:25 Thrift API version: 20.1.0
INFO  15:25:25 CQL supported versions: 3.4.0 (default: 3.4.0)
/custom-entrypoint.sh: line 20:    19 Killed                  /docker-entrypoint.sh "$@"

What can be a possible cause of that and how one would go about to fix it?