But the chief priests and elders persuaded the multitude that they should ask Barabbas, and destroy Jesus.
The governor answered and said unto them, "Whether of the twain will ye that I release unto you?"
They said, "Barabbas".
Pilate saith unto them, "What shall I do then with Jesus which is called Christ?"
They all say unto him, "Let him be crucified."
And the governor said, "Why, what evil hath he done?"
But they cried out the more, saying, "Let him be crucified."
When Pilate saw that he could prevail nothing, but that rather a tumult was made, he took water, and washed his hands before the multitude, saying, "I am innocent of the blood of this just person: see ye to it."
Then answered all the people, and said, "His blood be on us, and on our children."
Matthew 27 15-25
When St Matthew says that "all the people" cired out "Let (Jesus) blood be on us and on our children" he presumably means "all the people who were gathered outside Pilate's residence" -- "the multitude" who the Priests have persuaded to vote for Barabas and against Jesus.
He doesn't, so far as I can see mean "all the people in the middle- east" or "all the people in the whole wide world."
If we read this dispassionately, we would infer that Matthew thought that the responsibility for Jesus death lay with the mob who actually called for his death, not with the magistrate who sentenced him to death or the soldiers who executed him. We would take him to be saying that the consequences of this guilt would fall either on them (the people who actually called for Jesus to be killed) or on the next generation (their children).
We would also note that in the preceeding chapter, Jesus warned of an earth-shaking apocalypse which would occur within the lifetimes of those who had actually heard him preach. We would conclude that Matthew thought that Jesus thought that something very terrible was going to happen in Jerusalem within thirty or forty years of the death of Jesus. Say, around AD 70 or so.