Actually, they really weren't shocked. They had had little success against Robert E Lee's army.
At Chancellorsville the Army of Northern Virginia(Confederate) commanded by General Robert E. Lee engaged and defeated the Army of the Potomac(Union) commanded by General Joseph Hooker.
The union won
The Battle of Chancellorsville was due to the Union's attempt to defeat the Army of Northern Virginia and ultimately capture Richmond, the South's capitol. Although Union forces outnumbered the Southern forces, Robert E. Lee led his Army of Northern Virginia and defeated the Union army.
At the battle of Chancellorsville, it was General Robert E. Lee for the Confederacy and Joseph Hooker for the Union.
8,000
The Confederate Army of Northern Virginia led by General R.E. Lee defeated the Union Army of Potomac led by General Joseph Hooker.
About 4,500 men died for the Union side in the battle of Chancellorsville.
General Joseph Hooker (Union)
Chancellorsville
Of all arms, around 130,000.
Joseph Hooker
it was a battle during the Civil war between the Union And Confederate forces. Confederates won the battle.