WASHINGTON (Reuters) - President Barack Obama said on Monday that mass killings like the shooting rampage at a Sikh temple in Wisconsin were occurring with "too much regularity" and should prompt soul searching by all Americans, but he stopped short of calling for new gun-control laws. "All of us are heart-broken by what happened," Obama told reporters at the White House a day after a gunman opened fire on Sikh worshippers preparing for religious services, killing six before he was shot dead by a police officer. But when asked whether he would push for further gun-control measures in the...