Is it illegal to video someone without them knowing?

While at work another co-worker used an old cell phone to video what was going on after hours at work . I was clocked out of work. The video was me & another coworker making out. My job used this video and terminated both of us. They wouldn't let me view any of the video. I was only told I was recorded by another coworker & which coworker. Any advise would be appreciated.