Jn 19:34-37, Lk 23:26-27, Acts 2:36-38, Rev 1:7

In the Old Testament, the prophet Zechariah prophesied that the Israelites would mourn when they realized that the Jesus they had killed was the Christ. (Zec 12:10)

Zec 12:10 And I will pour upon the house of David, and upon the inhabitants of Jerusalem, the spirit of grace and of supplications: and they shall look upon me whom they have pierced, and they shall mourn for him, as one mourneth for his only son, and shall be in bitterness for him, as one that is in bitterness for his firstborn.

As the Old Testament prophesied about Christ, when Jesus died, His side was pierced with a spear, and none of His bones were broken. (John 19:34-36)

John 19:34 But one of the soldiers with a spear pierced his side, and forthwith came there out blood and water. 35 And he that saw it bare record, and his record is true: and he knoweth that he saith true, that ye might believe. 36 For these things were done, that the scripture should be fulfilled, A bone of him shall not be broken.

When Jesus' disciples saw Jesus' suffering, they mourned. (Luke 23:26-27)

Luke 23:26 And as they led him away, they laid hold upon one Simon, a Cyrenian, coming out of the country, and on him they laid the cross, that he might bear it after Jesus. 27 And there followed him a great company of people, and of women, which also bewailed and lamented him.

The Jews who killed Jesus mourned when they realized that the Jesus they had killed was the Christ. (Acts 2:36-38)

Acts 2:36 Therefore let all the house of Israel know assuredly, that God hath made the same Jesus, whom ye have crucified, both Lord and Christ.

37 Now when they heard this, they were pricked in their heart, and said unto Peter and to the rest of the apostles, Men and brethren, what shall we do?

38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.

When Jesus returns, those who do not believe in Him will mourn over their judgment. (Rev 1:7)

Rev 1:7 Behold, he cometh with clouds; and every eye shall see him, and they also which pierced him: and all kindreds of the earth shall wail because of him. Even so, Amen.