With the Overlord Guild gone, it was the turn of the Thunder Guild. The attack on the Overlord Guild was a surprise but that was not the case for the Thunder Guild. They were warned beforehand by their associates from the Overlord Guild.
The world may not know that these two guilds are allies but Chris knew that fact.
Even when the agency started to dig the information about Brian and when they found the deaths of those supers, they didn't find the link between these two guilds. The agency marked them as two guilds who chose to do things in a similar manner.
This was not uncommon. It was an established fact that both guilds were always at each other throats whenever possible. So they should be following similar tactics in many things.
No one from the outside world except for some key members knew that these two guilds were in fact allies.