Have you ever had to fire someone? Tell us about that event and the recordkeeping procedures you followed.
Your interviewer wants to be able to actually picture you in the human resources specialist job you're interviewing for. Paint that picture in broad strokes with all of the ins and outs of the activities you'd be expected to do, in this case your experience with termination processes and recordkeeping. In other words, connect the dots for the interviewer so that you're immediately recognized as a qualified and capable candidate. You can do this by framing your response more in terms of “I achieved“ rather than “I did”. Cite an accomplishment or group of activities from past employment that achieved a successful outcome even when the event it was a part of was negative in nature. Describe the situation without getting too bogged down in the process details themselves. Going through portfolio items such as performance reviews, references or complimentary correspondence will also add to your credibility.