Woman in White
A lore about a woman in white, or La Llorona, whose husband was unfaithful. When she found out, she'd kill her children who were fathered by her unfaithful husband. Then, out of grief of what she has done, she would take her own life, and come back as a spirt who kills any unfaithful man she comes across.
He thought he saw a woman in white standing over a bridge.