In many cases, there are computer selected searches mixed in with the "random" ones. I wouldn't want to assume that the group of Hispanics were intended to be "random".

What I have observed is that passengers with foreign passports on domestic flights tend to get flagged by the computers for screening. Perhaps that was the case this time?

The anecdotal evidence that the "random" screeners choose based on whatever personal grudge they have against a certain group of passengers is bothersome nonetheless.