Hello everyone ! Im here to give my point of view.
The Zombie Apocalypse
I think that the missiles that destroyed the Earth, didnt carry the element 115 and caused the zombie apocalypse, but instead initiated it. The destruction caused the weakness of the human civilisation's self defense against this new rising enemy. And also unleashed the zombies who were captured by organisations like Broken Arrow and others. Thats why you see that building called ''International Zombies Organisation''. It means that during the years 2000-2025, Zombies were already known in many countries. We can say that Zombies where captured there, and maybe experimented. The result is a new mutated creature, Jumping Jacks. It means that after the destruction, zombies came out from laboratories and start killing people. Humans weren't enough prepared due to the damage caused by the rockets, to counterattack and hold back the Element 115 Infection, which went airborne 2 years after the initial destruction and multiplicated the virus spreading. And which become a new global threat.
The Flesh was a group which was created on March 27, 2027, 2 years after the Earth Destruction. This group has been created to help the survivors feed themselves by eating zombies, due to the lack of food in the Earth. It's not rituals, but they start acting weird because they started hearing voices from Richtofen, one of the virus first symptoms. Richtofen is asking him to activate global polarizations devices to allow him to reach the Aether. During 10 Years, he found people but they always failed... Until that he meet our TranZit Crew.
The presence of the SDC in the building can be explained that they were in to control the infection, which occured in the nearby ''International Organisation'' building. They couldn't hold the zombies, they got infected, and now they are lurking and walking in what remains of Shanghai.