Pope Benedict XVI told pilgrims gathered in Vatican City's St. Peter's Square that he was "deeply saddened by Friday's senseless violence in Newtown, Connecticut".
The pontiff said, "I assure the families of the victims, especially those who lost a child, of my closeness in prayer. May the God of consolation touch their hearts and ease their pain".
"Upon those affected by this tragedy, and upon each of you, I invoke God's abundant blessings!", he added.
More top news
The vice presidential candidate was travelling with his wife, daughter and several campaign advisers, but no one was injured.
They deny a 'sweetheart deal' - but a senior source told ITV News the government promised to support such firms in the event of Brexit.
The father of Captain Khan, who died in Iraq in 2004, said the comment was "the most cruel thing you can say to grieving parents."