Despite the fact that those traveling across the Aqueduct were humble farmers returning home, Alves would lie in wait for them at nightfall, when he would rob them of their earnings.
Afterward, Alves would throw them over the edge of the 213-foot tall structure, sending them falling to their deaths. Between 1836 and 1839, he repeated this process some 70 times.
Local police initially attributed the deaths to copycat suicides, which led to a temporary closure of the bridge.
Alves then formed a group of bandits, before they were caught while killing four people inside the home of a local doctor, and Alves was arrested and sentenced to death by hanging.
But it's what happened next that makes this one of history's most interesting stories.
Scientists at the time wanted to study Alves' head, to determine the origin of his murderous nature. For this reason, they had his head removed from his dead body and preserved in a jar for study — where it has remained ever since.
This severed head now sits in the University of Lisbon's Faculty of Medicine where students can experience this chilling reminder of a horrifying man.