I ran nodetool decommission on a node from a 4 nodes cluster as follows:
nodetool -h 192.168.26.130 decommission 


But it never completes & doesn't show any messages, on seeing the logs I noticed:
java.util.concurrent.RejectedExecutionException: ThreadPoolExecutor has shut down
at org.apache.cassandra.concurrent.DebuggableThreadPoolExecutor$1.rejectedExecution(DebuggableThreadPoolExecutor.java:60)
at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:767)
at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecuto r.java:658)


on viewing netstats on this node I can see the node in LEAVING mode 
mode: LEAVING
Nothing streaming to /192.168.26.131
Nothing streaming to /192.168.26.129

Not receiving any streams.