A pest control company would be a better choice than a plumber, but the homeowner, probably a taxpayer, may have panicked and called 911 for help, especially if there were children in the home.
My father killed plenty of snakes with a shovel in our yard, but when he found a cottonmouth in his tool cabinet which kept moving from drawer to drawer via the back, he ended up calling for help since he couldn’t shoot it or whack it safely. A deputy arrived and dealt with it somehow. Happily, I was at work and missed out on all the “fun”.
When I was a boy, many many decades ago, We had an outhouse up the hill from our house. I hated to use it at night. One night I had to do number two really bad so I took a flashlight and went up there. As I sat on the ‘throne I kept hearing a hissing noise. When I finished the paper worki and opened the door, a king snake met me and he was ‘standing up tall, taller then me for sure. That poor snake had been under the outhouse during my visit. No wonder it was hissing at me!