Every mass shooting event in the United States recent years has been followed by debate about whether citizens with guns have or have not been successful in preventing or stopping such attacks. One example of the supposed effectiveness of armed civilians in halting such attacks has been bruited online ever since the December 2012 shooting at Sandy Hook Elementary School and involves a 1997 shooting at Pearl High School in Mississippi.
Example:
A 1997 high school shooting in Pearl, Miss., was halted by the school's vice principal after he retrieved the Colt .45 he kept in his truck.
In that 1 October 1997 incident, 16-year-old Luke Woodham stabbed his mother to death with a butcher knife in their home, then drove to his high school in Pearl, Mississippi, with a .30-.30 rifle, where he killed two classmates and wounded seven more. Woodham was apprehended in his car by Assistant Principal Joel Myrick, who confronted him with a .45-caliber pistol he had retrieved from own vehicle (Note, the meme image incorrectly identifies the site of the shooting as "Pearl River").
Holding up this occurrence as an example of an armed civilian's preventing (additional) shootings is problematic, however, for the same reason that nearly all such examples are: When a person is forcibly stopped before he can act, we can only surmise what that person would have done had he not been stopped; we cannot know for certain.
It's undeniable that Joel Myrick played a key role in apprehending Luke Woodham, but Myrick didn't prevent or curtail the shooting at Pearl High, as Woodham had already shot several people, broken off his attack, exited the school, entered the parking lot, and was attempting to leave the school in his car when he was finally confronted by the armed assistant principal:
After the shootings, Mr. Woodham, who worked at a Domino's pizza franchise, was captured by an assistant principal, Joel Myrick, while trying to leave the school in his mother's car. Myrick, 36, a commander in the Army reserves, sprinted to his own truck and retrieved the .45 automatic he kept there. Spotting Woodham near the parking lot, he shouted for him to stop. Instead, Woodham got into his car and tried to drive away, but he lost control and came to a stop as Myrick raced up to him. "I could see him sitting there, holding on to the steering wheel, his knuckles white, those glasses on him," recalls Myrick.Mr. Myrick, who was armed with his own automatic handgun, said that after he forced Mr. Woodham to lie on the ground and had his foot on Mr. Woodham's neck, the student's first words were, "Oh, Mr. Myrick, I'm the one that gave you the discount on the pizza the other night."
"I said, 'What? Why did you do this to my kids?'" Mr. Myrick continued. "And he said, 'Mr. Myrick, I've been wronged. The world has wronged me and I just couldn't take it anymore.'"
Putting the muzzle of his handgun to Woodham's neck, Myrick ordered him out and held him until police arrived.
The claims that Myrick's actions saved additional lives stem from reports that Woodham was on his way to Pearl Junior High School to continue shooting when Myrick subdued him, but he never admitted to having any such plans, and evidence documenting that he possessed such intent is not conclusive. One of the two victims whom Woodham killed at Pearl High School was his former girlfriend, Christina Menefee, and at his trial Woodham asserted that revenge against Menefee was the primary motivating factor behind the school shooting. Although Woodham might have continued venting his rage by shooting more people at another location, his professed motive was not consistent with the notion that he would have sought additional victims outside of Pearl High School.
It's possible Woodham could have driven to another school (or elsewhere) to continue shooting, and thus Joel Myrick did save an unknown number of lives by confronting him with a gun before Woodham could leave Pearl High School. But it's also possible Woodham also might have gone off somewhere and killed himself, or ditched his gun and tried to flee before being apprehended by authorities, or simply returned home and awaited his fate — as with all "What if ...?" scenarios, we can only speculate. But as for the facts of what actually happened (rather than guesses about what might have happened), Woodham was stopped only from leaving the scene after his shooting spree had already ended.
As for the usual claim that this event was something one would never "hear [about] in the mainstream media," Woodham's crime and his apprehension by Myrick were covered by such national news publications as The New York Times, People magazine, and USA Today, as well as a host of smaller news outlets.
Updates
Updated to indicate meme image incorrectly identified site of shooting.