going through the PreCheck line at DSM on a recent saturday morning at 5 am, I cleared the WTMD (no metal alarm) and 2 seconds later it beeped, TSA told me I was randomly selected for secondary screening, and directed me to the scanner. Informed them that I was opting out. As I waited for my "male assist", the next 2 people through the PreCheck WTMD also got the "random secondary alert". Random indeed.