Cannot get deleted comment id from JIRA's IssueEvent with type ISSUE_COMMENT_DELETED_ID

This question is about the atlassian JIRA plugin development. When I use event listener to handle JIRA's IssueEvent of comment deleted event, I can catch the comment deleted event with event type "com.atlassian.jira.event.type.EventType.ISSUE_COMMENT_DELETED_ID". But I don't know how can I get the comment id which has been deleted in this event. I've tried the IssueEvent.getComment for this situation, but it returns null.
BTW, I've tried the change log way to get the comment body of deleted from the change log, but the comment id is still missing and I don't know where to get it.