Of course there could be real trouble. You can never know. But personally I consider this video a theater of fear. If the guy staging the whole thing was an artist he should win awards.
A man does something strange, spilling a substance on a subway station. And not just any substance, a brilliant MacGuffin - mercury. The paranoia quickly kicks in and is very rich and complete.
"This could be a dry run for a terrorist attack" is the lead off, but we soon get truly paranoid responses like "There's no good reason to bring mercury onto a subway platform" (as if we need one to do anything). The man ("white or middle eastern", of course) is wanted for "questioning for an unexplained activity in connection with a possible act of terror". (I sure hope I'll never have to explain my activities. it would make sense to want him for scaring people and disturbing traffic first). The TV-heads agree that "it's a good thing we have those cameras in there so we can get an idea of what's going on" (nothing really happened) but still "all these security systems are really starting to pay off" and the conclusion: "Are we being too careful? Experts say there's no such thing" (of course there is).

There's something wrong with how society mimics our own neural danger response. Society doesn't have a good mechanism to get rid of the fear again. No dreams, or forgetful filter to keep us sane. On the contrary, there's all kinds of subsystems of the hive mind with a strong interest in keeping the fear going.