The article is snippets of information with little context, implying links between them where there aren’t necessarily connections, at least based on the currently available information.
There’s no suggestion he went to the school in question. He didn’t go directly from the sect to the military - the Post article which the guardian is lifting heavily from says “Bushnell was raised in a religious compound in Orleans, Mass., on Cape Cod, according to Susan Wilkins, 59, who said she was a member of the group from 1970 to 2005. She said that she knew Bushnell and his family on the compound and that he was still a member when she left. Wilkins said she heard through members of Bushnell’s family that he eventually left the group.” So she knew him when he was 6? We have no idea what age he was when he left though the article suggests it was when he was young: “Wilkins’s account is consistent with those of multiple others who said Bushnell had told them about his childhood in the religious group”.
He also didn’t go from military to anarchy - the Post again says “Lupe Barboza, 32, said she met Bushnell in San Antonio in 2022 at an event for a socialist organization. She said they bonded over their politics and started working together to deliver clothing and food to people experiencing homelessness.”
As for the anonymous anarchist friend, “Bushnell, 25, mentioned nothing violent or self-sacrificial, the friend said.”
I don’t see how his final calls, texts or “will” speak to his mental state. I’m sure more will come out in the next few days about him. If he was suffering from severe mental health it seems the deterioration was extremely rapid given the description of him singing karaoke at his leaving past just last month.