On 27 Februrary 1933, an attack on the Reichstag Fire happened. The Reichatag was set... On fire... And the perpetrator was just one guy known as van der Lubbe. He was identified as communist.
Some historians doubt the legitimacy since this is very convienient for Hitler. He declares a state of emergency and got Hindenburg to issue the "Decree for the Protection of the People and State". He also called for another election! Hitler used the decree to suspend civil rights and allow the police to turn attention away from the SA.
Next we have the totally unbiased election in 5 March 1933 which gives Hitler 288 seats. He then banned the Communist Party (he was justified by the Reichstag Fire) so they couldn't take up 81 seats. He then forms a coalition with nationalist parties to form a two-thirds majority (thus bypassing the Reichsrat).
The Enabling Act is then passed in March 1933. This law allows Hitler to basically do what he wants for four years. He starts by removing all challenges to his leadership.
The first thing he bans is trade unions. This is because the failure of the Kapp Putsch was due to strikes and Hitler didn't underestimate the worker's power. Then in July 1933, he bans all political parties thereby making the Nazi party the only party in Germany. He then centralises Germany by banning all local governments (since they can pass laws under their own jurisdiction). He appoints his own governors as leaders of each region.
Now that Germany is a one party state, he needs to ensure he's the leader of it. Ernst Rohm was the leader of the SA which had developed a threatening loyalty to him. So Hitler ordered his execution and several other officers on 30 June 1934. This is the Night of the Long Knives.
Von Papen, the vice chancellor, was then placed under house arrest. The SS squads shot his press secretary and other staff. The next four days were a bloodbath. 400 people were shot without trial incuding von Schleicher and Gregor Strasser (a member with similar views to Rohm).
The SA were allowed to continue afterwards but were placed firmly under control.
Then on 2 August 1934, Hindenburg died at 87 (not murdered). Hitler declared himself as a Fuhrer and gave a plebiscite to confirm this. With the help of propaganda, 90% of Germany agreed and Hitler became a dictator.