I'm sorry, I couldn't resist.
—Schultz, moments after he killed Candie and before his death
Dr. King Schultz (early 1800s - May 5, 1859) was a dentist-turned-bounty-hunter who freed Django and helped him rescue his wife. Schultz was eventually killed in a shootout when he shot Calvin Candie in the chest with his ladygun. It's estimated that Schultz is in his late 40's to early 50's during the events of the movie.
King Schultz came from a wealthy family in Germany (presumably Düsseldorf, Rhine Province, Kingdom of Prussia) and is highly cultured as well as very intelligent. He practiced dentistry up until 1853. Schultz despised slavery and hated the sight of slaves being treated poorly and also killed. At some point in his life, Schultz was married. His wife supposedly died of an unknown cause, as we can see a tombstone with the name of Paula Schultz in Kill Bill II, who lived from 1823 to 1893. Schultz became a bounty hunter in 1853, potentially due to the murder of his brother (referenced in the song His Name Is King, featured in the film's soundtrack), and it is thought that his hunt for his deceased sibling's killer set him on this career path. While tracking down the Brittle Brothers, Schultz came across the Speck Brothers and their slaves who were marching the country for days. Schultz claims he is looking for a slave who knows the Brittle Brothers and the Specks allowed the former dentist to inspect the slaves. When Schultz came to Django who was originally owned by the Brittle Brothers, the Specks refused to sell him and grew impatient with Schultz. When Ace Speck threatened Schultz to go away, Schultz kills Ace and crippled Dicky Speck by shooting his horse. Shultz then frees Django and gave the other slaves 2 choices. 1: Lift up the dead horse and carry Dicky to a nearby town which was miles away from where they came from or 2: Kill Dicky and have their long desired freedom. The slaves picked the second choice.
Hours later, Schultz and Django head to a nearby town and settle at a bar in which the innkeeper runs away for help. Schultz humorously suggests that the innkeeper calls in the sheriff rather than the marshall. After killing Sheriff Bill Sharp, Schultz and Django were then greeted by the armed residents and the marshall himself. Schultz uses a clever advantage to prove that he is in fact a bounty hunter and Django is a freeman. After dealing with the sheriff, Django tells Schultz about his time with the Brittle Brothers and Schultz promises Django freedom and payment for his service. Schultz then finds out that Django is married. Traveling from Texas to Tennessee, the duo went to the Bennet Plantation where the Brittle Brothers are currently located. At the plantation, Spencer G. Bennet, the owner harrasses the duo because Django has the priviledges that a white man has. Schultz manages to cool Bennet's attitude by offering him money and telling him that Django is a freeman. While Django deals with John and "Little Raj" Brittle. Schultz rushes to Django and asks him of Ellis's location. Django points him to the fields and Schultz snipes down the last Brittle. Approached by an angry mob that is lead by Bennet, Schultz once again uses his clever advantage to get rid of Bennet and his angry mob.
Schultz became aware that Bennet will hunt him and Django down so Schultz set up a trap for Bennet and his mob to come. Before hiding, Schultz puts a pack of dynamite in the dentist sign. As Bennet and his mob came, they started to madly search for the bounty hunters but far from the dentist wagon, it is shown that the duo are seen on top of a tree, with a rifle in Schultz's hand. Schultz then ignites the dynamite by shooting the dentist sign which killed almost all the supremacists. The remaining survivors fled in terror while Bennet struggles from his horse. As Bennet is escaping, Schultz offers Django to shoot Bennet to which he complies. Django then successfuly snipes Bennet to which shows Schultz being proud of Django and also surprised of his marksmanship.
Proud of Django's skill, and reluctant to let him risk his life by attempting to rescue Broomhilda on his own, Schultz turns Django a full freeman, but offers him to join the bounty hunting business until the snow melts, with himself as his mentor. Django eagerly agrees, and becomes not only an expert shooter, but also an incredibly quick thinker.
Once winter is finally over, Schultz accompanies Django to Mississippi, where the auction in which the latter and his wife had been sold and separated took place. After a quick research, they learn Broomhilda has been sold to Calvin Candie, the violent owner of Candyland plantation. Schultz suggests tricking Candie into leading them to the Big House (in order to confirm he is still in possession of Broomhilda) by offering to buy one of his trained Mandingo fighters for $12000, while Django poses as an expert in Mandingo fights who is hired by Schultz in order to help him pick the right fighter. Leonide Moguy, Candie's lawyer, introduces Schultz and Django to the renowned slaver during a bloody fight between slaves Big Fred and Luigi. The dentist's plan is set into motion with no inconvenients.
During a carriage trip to Candyland's Big House, Schultz witnesses D'Artagnan's cruel execution, and is visibly upset by it. When him and Django arrive to the Big House, Schultz requests for Broomhilda to be delivered to his room at night, claiming he wishes to speak in his language with somebody else. When the two of them meet, Schultz informs Broomhilda of his plan, and allows her and her husband to reunite briefly. The next day,in the dining room, Schultz tells Candie he may want to buy Broomhilda along with the fighter. However, his cover is blown when Stephen realizes Broomhilda knows Django. He informs Candie of the bounty hunters' plan, to which the slaver reacts by threatening to kill Broomhilda unless Schultz pays the $12000 he had initially offered for the fighter. Desperately, the German pays the agreed amount, freeing Broomhilda from Candie's possession. However, flashbacks of D'Artagnan's death, along with all the cruelty displayed by Candie continue to disturb Schultz, so he decides to leave Candyland as soon as possible. Out of no desire but to mock him, Candie asks Schultz to shake his hand, as a way of closing the deal. The German refuses, but when the slaver threatens to kill Broomhilda, Schultz pretends to yield and walks towards Candie with his arm extended. Much to Candie's surprise, however, Schultz doesn't shake his hand, but instead pulls out the concealed lady gun he had used to kill Sharp and shoots him in the chest, killing him. Knowing that action would cause his death, Schultz turns to Django and simply tells him he was unable to resist. Butch shoots and kills him with his shotgun, triggering the Candyland Shootout. After the shootout, Dr. Schultz is mentioned by Django being his partner in their adventure (which is later confirmed by the other slaves) to the LeQuint Dickey Mining Company (a group he was sold to). After escaping, Django finds Schultz's corpse in a barn and collects the papers in his pocket. Django then bids farewell to his fallen friend. Later that night, Django blows up Candyland and Dr. Schultz appears in a flashback, calling him "the fastest gun in the South."