Destruction of Luke Skywalker's Jedi temple

"He was training a new generation of Jedi. There was no one else left to do it, so he took the burden on himself. Everything was going good, until one boy, an apprentice, turned against him and destroyed it all. Everything Luke had worked toward: gone. Luke felt responsible. He walked away from everything."

- Han Solo

The massacre of a new generation of Jedi, trained by Luke Skywalker, occurred in the years after the Galactic Civil War. It was carried out by Knights of Ren, a group of Dark side followers lead by Kylo Ren. The massacre left Skywalker's attempt to rebuild the Jedi Order in tatters, and the Jedi Master went into exile for years before he was found again by a young Force-sensitive named Rey.

Prelude
At the end of the Clone Wars between the Galactic Republic and the Confederacy of Independent Systems, the Sith Lord Darth Sidious&mdash;secretly the Republic's Supreme Chancellor Palpatine&mdash;took fallen Jedi Knight Anakin Skywalker as his apprentice. On his master's command, Skywalker, who was given the name Darth Vader, marched on the Jedi Temple on Coruscant and began the eradication of the Jedi Order, while Sidious executed a command to the clone troopers of the Grand Army of the Republic to kill the Jedi. The Jedi were branded as traitors of the Republic, and, with the Jedi Purge leaving the Jedi unable to stop him, Sidious transformed the Republic into the Galactic Empire, with himself as its sovereign ruler.

Over two decades later, Vader's son, Luke Skywalker, trained as a Jedi. The end of the Galactic Civil War saw the redemption of Anakin Skywalker and the end of the Sith, as Anakin killed the Emperor during the Battle of Endor. Luke was the last known Jedi and, as per the wishes of his late Jedi Master Yoda, he began training a new generation of Jedi Knights. One such Jedi was his nephew, Ben, the son of Skywalker's sister Leia Organa and the smuggler Han Solo. Organa and Solo chose to send their son to Skywalker for training because he struggled with the dark side of the Force, much as his grandfather, Darth Vader, had once done.

The massacre
Despite Skywalker's attempts to help his nephew, Ben fell under the influence of a dark Force user called Snoke, the Supreme Leader of the First Order. Ben became Kylo Ren and killed the Jedi that Skywalker had been training. This earned Kylo the nickname of "Jedi killer."

Aftermath
The Jedi massacre left Skywalker's dream of rebuilding the Jedi Order in ruins. Blaming himself for what had happened, the Jedi Master went into exile and vanished from the galaxy, though those closest to him believed that he went off in search of the First Jedi Temple. A partial map to his location was contained in the memory systems of his astromech droid, R2-D2, who had remained in low power mode ever since his master had disappeared. During the conflict between the First Order and General Organa's Resistance, Poe Dameron traveled to the desert planet Jakku and found the remainder of the map to Skywalker's location. The information was given to him by Lor San Tekka, a member of the Church of the Force who believed that balance could not be brought to the Force unless the Jedi Order returned. That information was placed into Dameron's astromech droid, BB-8, and was eventually brought to the Resistance. After R2-D2 regained power and the two sections of the map were combined, Skywalker's location was discovered. Rey, a young Force-sensitive&mdash;one who had seen glimpses of the Jedi massacre's aftermath in a vision&mdash;found Skywalker on the world where he had been hiding.

Behind the scenes
The massacring of Luke Skywalker's Jedi was referenced in the 2015 film Star Wars: Episode VII The Force Awakens. Although the event took place in the film's backstory, its aftermath was briefly seen in Rey's vision.

Appearances

 * Star Wars: Episode VII The Force Awakens
 * Star Wars: Episode VII The Force Awakens novelization
 * Star Wars: Episode VII The Force Awakens junior novelization