system
A chat on subreddit /r/wallstreetbets
human
From the Article:

“Trading in dozens of stocks on the New York Stock Exchange was halted shortly after the market opened on Monday after an apparent technical issue.

The major stocks impacted included Morgan Stanley, Verizon, AT&amp;T, Nike and McDonald’s, according to the NYSE’s website.”
gpt
Also UPS. Registered as down 8+% then back to almost break even.