What does Arc Flash look like?

[derekleffew]

From Injured workers transferred to burn center :

Two United Launch Alliance employees seriously injured in an electrical explosion at Vandenberg Air Force Base have been transferred to a hospital that specializes in treating burn patients.
...
They were injured Saturday in what was described as an “arc flash” while working at Space Launch Complex-6 on South Base.

I can't imagine a scenario whereby an arc flash occurring near a rocket could ever be good.