Excellent example of a reason to screen beyond "middle eastern looking."
He was 40/50ish, dark, bearded, dressed in dark unpressed clothes and had a small satchel. He kept that bag close, between his legs, and sat straight up in his seat, looking straight ahead or down. I mean, he really stood out! My mind was filled with all kinds of scenarios. On the flight, he sat quietly and I never saw him get up. I didn't see the bag.
When we got to San Francisco, I last saw him surrounded by family (who looked just like him) and he was smiling and talking away! LOL! My fertile mind had judged a perfectly innocent traveler. Lesson learned.