“I made a killing in the stock market today—I shot my broker”

The term “to make a killing in the (stock) market” means “to make a lot of money” and dates to at least 1913. A joke with the term “market” surfaced by 1956: “Peter Lind Hayes knows a chap who made a killing in the market. He shot at the manager of a chain store.”
 
A stockbroker was added to the joke (used by comedians Groucho Marx and Bob Hope) by at least 1958: “Groucho waved them aside with ‘I once made a killing in the market. I shot my broker.’” Another version is: “The market opened with a bang. I shot my broker.”
 
   
17 October 1913, Syracuse (NY) Herald, pg. 20, col. 4:
His comrades looked at him with envy and awe, believing he had profited by a tip to make a killing in the market.
   
Google News Archive
3 April 1929, Montreal Gazette, pg. 3, col. 1 ad:
He made a “killing in the market”—BUT!
(Crown Trust Company—ed.)
 
16 October 1956, Quebec Chronicle-Telegraph, “Daily CHuckle” by Bennett Cerf, pg. 4, col. 4:
Peter Lind Hayes knows a chap who made a killing in the market. He shot at the manager of a chain store.
   
24 November 1957, Los Angeles (CA) Times, “The Lass Roundup” by Bennett Cerf, pg. L4:
In Tacoma, Wash., a dear young girl made a killing in the market. She shot the manager of the meat department.
 
11 May 1958, Chicago (IL) Tribune, ‘Radio_TV Gag Bag” by Larry Wolters, part 8, pg. K63:
Groucho waved them aside with “I once made a killing in the market. I shot my broker. And not a moment too soon. He was about to commit suicide.”
 
Google News Archive
7 January 1960, Ocala (FL) Star-Banner, “Hollywood Today!” by Erskine Johnson, pg. 7, cols. 1-2:
Frank Gorshin says he made a killing in the market—he shot his broker.
 
7 June 1962, Idaho Falls (ID) Post-Register, Earl Wilson column, pg. 27, col. 3:
TODAY’S BEST LAUGH: Dave Barry says he just made a killing in the stock market: “I shot my broker.”
 
31 January 1967, Los Angeles (CA) Times, “Strange Interlude—Buyer, Seller and Tape Recorder,” part II, pg. A6:
Overheard in a downtown coffee shop, one man to another: “I made a killing in the stock market today-I shot my broker!”
 
Google Books
The Modern Handbook of Humor
By Ralph Louis Woods
New York, NY: McGraw-Hill
1967
Pg. 58:
Wall Street tells about the trader who made a killing in the market. He shot the manager of a Grand Union store.
   
Google News Archive
18 July 1970, Toledo (OH) Blade, “Top Joke Topics Were Sex, Business, Strikes And Spiro” by Earl Wilson, pg. 9, col. 3: 
Bob Hope said, “I made a killing in the market today—I shot my broker.”
 
Google Books
The Show Business Nobody Knows
By Earl Wilson
London: W. H. Allen
1972
Pg. 106:
Twenty years ago you might have heard Bob Hope say from some theater stage, “I made a killing today in the market—I shot my broker.”
 
Google News Archive
9 October 1975, Beaver County (PA) Times, “New recession, same old jokes” by Earl Wilson, pg. B8, col. 1:
NEW YORK—The American sense of laughter is holding out strong against the recession, depression, or whatever it is, and political crises. The Show Business audiences still smile when a comedian says, “the Stock Market opened with a bang this morning—I shot my broker.”
 
There was the same joke in the 1929 Crash—exvept that it started, “I made a killing in the market today.”
 
Comedy Quotes from the Movies:
Over 4,000 bits of humorous dialogue from all film genres, topically arranged and indexed

By Larry Langman and Paul Gold
Jefferson, NC.: McFarland
2001
Pg. 313:
Second-rate comic Rip Taylor picks up hitchhikers Cheech Marin and Thomas Chong and regales them with some of his best material: “I just made a killing in the market—I shot my butcher.”—

(1982)