If something like this happens across your local night sky, anxiety might be a reasonable reaction.
This was the scene last night above Los Angeles and the internet has been suitably riled up in the hours since. The corresponding hashtag, Facebook tells me, is #UFO. Which indicates that the source of said anxiety is UFOs and not rockets, which is weird. The thing is clearly a rocket and Earth-bound humans have lots of rockets. For that matter, rockets are capable of doing way freakier stuff to the sky than this thing. Remember this? It occurred over Norway in 2010, the result of a rocket.
The thing in the first picture is from a naval test fire launched off the California coast, according to the Los Angeles Times. It was a scheduled event and anticipated to the point that air traffic in and out of LAX has been diverted away from offshore approach lanes for the next several nights. Presumably there will be more later in the week.
If I hadn't read the news and was the paranoid type (OK, I am) my first thought would probably be the much more reasonable fear of imminent nuclear vaporization. There are no aliens, but we still live in a world with around 4,000 currently deployed nuclear weapons and over 15,000 in total.
It doesn't take a streak across the night sky to be terrified of that.