After working briefly for Keyes Realty, he got a full-time job as a history teacher at Hialeah Junior High School in 1962[2] and moonlighted at Miami-Dade Community College as an accounting instructor from 1964 to 1970.

There he taught American history until March 3, 1982, when he was relieved of his teaching duties for medical leave to treat his psychiatric problems.

Though neighbors described Brown as a quiet, kind and helpful man, who was working hard to keep his duplex neat and clean, and praising him overall as a landlord, it was also said that he made a habit of walking into other people's yards early in the morning, waking them by yelling "United States!"

It was also reported that he once broke a window when firing a pellet gun, and picked grapefruit from a neighbor's tree wearing only his underwear.

The school board's director of personnel control, Pat Gray, described this as "a classroom incident...wherein Mr. Brown demonstrated a significant lack of adult judgment, an overtone of sexual fixation, and definitive aggression toward students."

I, also, fear for the safety of the students since during my conference with Mr. Brown he demonstrated no regret for his actions pointing to the fact that he is a 'man' and any man would have reacted in the same manner."

Brown reacted by writing a response in which he suggested that the principal "should seek the help" of the school board's employee assistance program, to which he himself was referred to in January 1982.

[4][7] On August 19, the day before the shooting, Brown had a heated argument with Jorge Castalleda, an employee at Bob Moore's Welding & Machine Service Inc., about a $20 bill for repairing a lawnmower engine he wanted to use to power his bicycle, saying the work was poorly done.

Early the next day Brown went to a gun store a few blocks from his home in Hialeah and purchased two shotguns, a semi-automatic rifle and ammunition.

An hour before starting his rampage, Brown invited his 10-year-old son to join him in "killing a lot of people" telling him that the final destination would be Hialeah Junior High School.

According to police, Brown walked through the building methodically shooting everyone, most of the time at close range and sometimes twice, leaving three victims in the office and others in the work area and the driveway in front of the shop.

In the end, six of the eleven employees present were dead and two more dying, while three who were injured managed to escape and jump into the car of a passing motorist, who took them to a gas station a mile away and called for help.

Out of ammunition, Carl Brown left the store, got back on his bicycle and started cycling away, apparently towards Hialeah Junior High School.

When Mark Kram, an employee at a nearby metal shop, was told of the massacre, he grabbed a .38 revolver and set out to pursue the shooter in his car.