must have been
It must have been someone else.
Tu muerte no habrá sido en vano.
Your death will not have been in vain.
Oh Señor, me pregunto quién habrá sido el primer tonto que inventó los besos.
Oh Lord, I wonder who the first fool to invent kissing was.
That must have been terrible.
No sé cuál habrá sido su experiencia con las turistas americanas.
I don't know what her experience with American tourists was like.
— Locuras de verano (1955)