Herschel Grynszpan was the 17-year-old boy who triggered Kristallnacht.
His parents were Jewish Poles who had been exiled from Hanover, Germany, to Poland. Poland refused to admit them, and they were left stranded at the German/Polish border. All their possessions were stolen and they were reportedly starving to death (which turned out to be untrue). Enraged upon hearing of this from relatives, Herschel bought a gun and walked into the German embassy in Paris, where he was living at the time, looking for the ambassador. Instead he ended up killing a minor functionary named Ernst vom Rath, on November 7, 1938, by firing three bullets into his abdomen. Nazi Germany retaliated two days later by burning synagogues, destroying Jewish shops, beating up and murdering Jews and deporting an estimated 25,000 to concentration camps. Ironically, his parents had sent him to Paris for safety in 1936, though while there he encountered anything but safety in the face of widespread anti-Semitism. His parents survived the war.
Herschel was awaiting trial in Paris when the Germans took the city in 1940. With other French prisoners, he was sent to Vichy territory, from which he was surrendered to the Germans as soon as they asked for him. Joseph Goebbels wanted to stage a show trial, using Herschel as a symbolic centerpiece to "prove" that Jews were the cause of hardship in Germany. Hershel refused to play along, claiming (falsely) that the assassination grew out of a homosexual liason. This made the show trial impossible and would've been a major embarrasment for the Nazis.
He was never tried, and most people assume he was summarily executed or starved to death in captivity but no records exist of his passing so it is possible that he survived. Historians seem to agree that he spent some time as an inmate at the Sachsenhausen concentration camp. Adolf Eichmann testified during his war crimes trial in 1961 that he had briefly talked to Grynszpan in late 1943 or early 1944, but that afterwards Eichmann knew not what became of him, and he was never seen or heard from again.