That last quote is often misremembered as "I'm in charge here" — including by the BBC in its obituary today — for, yes, Alexander Haig has died. (He was 85.) Here's another obituary. And here's the NYT:
[The day of the Reagan assassination attempt] Secretary of State Haig wrongly declared himself the acting president. “The helm is right here,” he told members of the Reagan cabinet in the White House Situation Room, “and that means right in this chair for now, constitutionally, until the vice president gets here.” His words were tape-recorded by Richard V. Allen, then the national security adviser. His colleagues knew better. “There were three others ahead of Haig in the constitutional succession,” Mr. Allen wrote in 2001. “But Haig’s demeanor signaled that he might be ready for a quarrel, and there was no point in provoking one.”
Mr. Haig then asked, “How do you get to the press room?” He raced upstairs and went directly to the lectern before a television audience of millions. His knuckles whitening, his arms shaking, his knees wobbling, Mr. Haig declared to the world, “I am in control here, in the White House.” He did not give that appearance.