In 1927, a diversionary fire at a Michigan farm carried a stenciled sign reading "Criminals are made, not born." This deep dive traces the life of Andrew Kehoe, the farmer and school board treasurer behind the deadliest act of mass murder at an American school, the Bath School disaster.

We follow Kehoe from his electrical engineering training and a severe 1911 head injury through his failing farm, mounting grievances, and public political defeat, examining how a rigid, controlling mind planned a months-long attack that killed 45 people, most of them children, before he detonated a truck bomb that killed himself and the superintendent.

• How a two-week coma and frontal-lobe injury may have reshaped his personality
• The suspicious stove explosion that killed his stepmother Frances
• His use of surplus pyrotol and his acc ...