Doomsday Protocol: Catastrophe Strikes, First Move—Eliminate the Pretender

Tick.
The second hand on the wristwatch moved a minuscule increment.
In the back row by the window of Class Three, Grade Eleven, Chen Yi suddenly opened his eyes and glanced at the time on his watch.
7:15.
He took a deep breath, forced himself to remain calm, and looked out the window.
Suddenly, a blazing sphere of light burst forth in the sky, its intense radiance instantly consuming everyone's vision.
Chen Yi closed his eyes and silently began to count.
From ten to one—when his mental countdown reached zero, the sudden light vanished, and the clamorous cries of his classmates filled the air.
Chen Yi drew a long breath.
He pushed aside his desk and chair, then strode out of the classroom.
Eighty-one steps forward, then he turned and went downstairs. At the corner of the staircase, he stopped, wrapped his hand in his school jacket, and smashed the glass of the emergency fire window.
Reaching in, Chen Yi gripped the sharp fire axe with his left hand.
He exhaled heavily, then swung the axe behind him with force—a sickening crack as the blade struck bone, and a snarling zombie was decapitated.
...
No one knew that Chen Yi was from the future.
No one but himself.
The sphere of light that had suddenly appeared in the sky seemed, in that instant, to rob Blue Star of all its heat and light for the next hundred years. Deprived of energy, Blue Star became the cradle of humanity’s worst nightmare.
That ball of light, which flared at seven in the morning, vanished as quickly as it appeared, sw