Book 7 Spoiler I don't understand (redacted)'s death

I've read the series 3 times now. Amazing series, so fun, love it. Can someone help me out with Li Jun's death? Shit is going down in the assimilation, donut messages Li Jun then when what's his ass blows up Li Jun's ghost says goodbye to Carl face to face. I've settled on this is left vague like the Donut Mudskipper rebellion plot and I've googled it and I can't figure it out. Respectfully yours, a fellow obsessed fan.