What to do now.
Gao Guang does not have the authority to command princes by capturing the emperor.
However, employing the historical lesson of fulfilling one's mission can be useful. This is neither one of the Thirty-six Stratagems nor a tactic from The Art of War by Sun Tzu, but knowing this idiom from middle school is enough.
Tang Ju fulfilled his mission without disgrace, the emperor's wrath led to blood flowing like streams, and a common man's wrath spattered blood five steps away.
Knowing the meaning of these idioms, one knows how to handle the current situation.
Gao Guang is not exceptionally clever, but he knows how to handle such matters; this is called ancient Eastern wisdom.
In Western terms, it is considered having mature case references to draw from.
Ensuring mutual destruction is a necessary precondition for peace.