An account of the crucifixion of Christ was written hundreds of years before he was born. The account of that event, of fulfilled prophecy, is recorded in the four gospels.
How do we know that prophecy was really written before Christ? In the second century BC the Hebrew scriptures were translated into Greek. This was a big enough deal that this is recorded outside of the Bible itself.
If this is true, then we only have to establish whether Jesus, through the crucifixion, deliberately set out to fulfill this prophecy, or whether the gospels set out to copy it. Neither of these options makes sense when you understand that a crucified Messiah was not what anyone was expecting. All of the Jewish leaders, and even Jesus's close disciples, expected the Messiah to take power from the gentile nations and return ruling power and land to the Jews as God's people.
This is only one of many prophecies that were fulfilled in the person of Jesus Christ.
Try reading Psalm 22 (written 1000 years before Christ) and picking out the parts that were also in the gospel accounts. If you get stuck, start at verses 16 to 18.