My guess is that the 2 cats were already squaring
off for a fight outside before one them tried getting
away, finding an open door to sneek into.
The other cat followed, and neither cat knew the
people, so they also took them as potential threats.

What also isn't addressed is whether any of the people
tried grabbing or pushing the cats back outside.
As the boy I believe had cuts and bites on his face,
I would tend to think he picked one up, as cats generally
don't jump all the way up into ones face.

Under such circumstances, it's best to stay away from
them or put yourself behind a door if you don't
know how to handle cats that are in a fighting situation.

(A cardboard box or blanket tossed over them is a good
way of control, and a cup of water tossed at them is good
for distraction or repelling.
If you have to grab them, it's best to have leather gloves
on, and maybe even a leather coat.)

The story I read only had one of the cats captured,
so I assume one got away.