A man who had previously tried to join the Islamic State group rampaged in Vienna armed with an automatic rifle and a fake explosive vest, fatally shooting four people before he was killed by police, Austrian authorities said Tuesday. Video that appeared to be from the scene showed a gunman, dressed in white coveralls, firing off bursts seemingly at random as he ran down the Austrian capital’s dark cobblestone streets. While the attack lasted just minutes, authorities said only on Tuesday afternoon that there was no indication of a second attacker — adding to tension in the capital as residents were urged to stay home.