To answer your question, you change the issue - that will fire an event. Although I'm really not sure I understand the question at all.
However, the task is clear, and very easy. You'll need a plugin that provides "set custom field to current user" as a post-function on the "close" transition. There's one in the /Jira Suite Utilities that lets you set any custom field and provides a %current user% option for setting user-picker fields. I would (and do) use that one.
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
We're bringing product updates and pro tips on teamwork to ten cities around the world.Save your spot