Attempted assassination of President Trump: Who is responsible?

You've heard the news. You may be watching the news right now. About 75 minutes ago someone shot Donald J. Trump, the once and future POTUS, during a rally in Butler County PA. 

Your immediate reaction, like mine, must surely have been: who did this? That's a question which may never be answered!

10 minutes ago I watched, on NBC, a live interview with a person who said she was sitting right in the front row. After she confirmed what we saw in the video, the interviewee said "Thank God they killed rthe shooter", who she said had fired from a tower somewhere to the right Mr Trump.

Strange, isn't it, that no official source had said anything about that. Immediately the interview concluded, Lester Holt said that this was just the account of one person which could not be confirmed. Has a cover-up already begun?

Let's suppose that the shooter was (a) an Islamic (or other) terrorist; (b) a looney leftist, antifa type; (c) an agent of the Deep State; or even (d) a sufferer from TDS, nuttier than squirrel shit and determined that there should be no second term for Trump. Would the Deep State, the Democrats and their lickspittle media want you to know this?

If they want to cover their sorry asses, how would they do so? Simple. By assassinating the would-be assassin. So far, what we're hearing from Official Sources is that the threat has been "contained". Whatever can that mean? Stay tuned... but don't hold your breath!

UPDATE ADDED at 1930: It is now four hours since the failed assassination attempt. The shooter is dead, having been shot by a Secret Service sniper within seconds of shooting at President Trump from "an elevated position" (read: tower) about 200 yards from the podium (yet somehow outside the secure perimeter). 

The body of the shooter has been recovered, along with his AR-15 assault rifle, but he remains unidentified. More accurately, no-one is prepared to tell us what the government knows. Commentator on CBS to interviewee: "You've called this an 'attempted assassination'. Surely you're not implying that the government was somehow involved... are you?" Interviewee: "Oh no. No no."