Process was intentionally killed - now the process is still showing in "show processlist "

We had a MariaDB long-running process (40 hours), so I killed the thread. But, the thread is still there, with: - showing Command as Killed. - a State of Unlocking tables. - Info is insert into ... What does this mean? More importantly, how do I get rid of it? It's been over 31 hours since the thread entered the "Killed" state. UPDATE: We restarted the container running MariaDB. There was no indication of anything wrong but... Would it make sense to recast this thread to be now about how to check for errors in the database (My MariaDB skills are rudimentary) or should I start a new thread?