I hadn't done many interviews before starting at my current job, where they seem to make a point of getting a lot more people involved in the interview process.

I hadn't done many interviews before starting at my current job, where they seem to make a point of getting a lot more people involved in the interview process. I guess this is an idealistic view, but it should be pretty clear if you're a hiring manager whether the people you're getting involved in the interview process are likely to be jerks to a candidate. What you describe is embarrassing, and does reflect poorly on your company. Review sites like Glassdoor do or did have interview reviews as part of their company review, and people do go look at those when deciding whether to apply at a company. I hope you shared your feedback with your coworker, and also the hiring manager. That coworker is probably not ready to do interviews and needs some training (or maturing) first. In the future, you might interrupt the coworker and then try to help the candidate along; maybe they won't pass the interview, but you don't have to let them leave feeling like a failure, and along the way you might get some information about where they could fit in your organization. And the entire interview won't have felt like such a waste.