It’s terrifying to look at photos of innocent children… and then realize that some of them grew up to become mass murderers.

We’re wired to see kids as pure, sweet, and untouchable. That’s why seeing a smiling baby and knowing they later committed unimaginable crimes hits so hard.

And the seemingly sweet, innocent child we’re about to introduce would one day grow into one of the most terrifying killers in American history.

On a warm day in May 1960, a baby boy was born in Milwaukee, Wisconsin. His parents — a 23-year-old chemistry student and a 24-year-old teletype machine instructor — welcomed their first child with hope and dreams for his future.

By all accounts, he was a lively, cheerful boy in his earliest years, full of energy and promise. But something changed.

Shortly before his fourth birthday, he underwent double hernia surgery, and his family noticed an immediate shift in his behavior. The once-bubbly child became quiet, withdrawn, and increasingly uneasy.

Resentment toward his baby brother

By the time he started school at six, the boy was reportedly already grappling with feelings of abandonment and had begun to harbor resentment toward his baby brother. Teachers described him as timid and reserved, often sensing feelings of neglect as his father’s studies kept him away and his mother battled depression and hypochondria.

The household was tense. Arguments between his parents were frequent, and his mother even attempted suicide at least once, demanding constant attention and spending much of her time bedridden. The boy later admitted that he never felt his family was stable, never sure if his home would remain intact.

However, the thin, blonde-haired boy did have a few friends growing up.

“He was a fun kid to be around as a child,” said Ted Lee, who grew up in the same neighborhood.