Booth had planned to abduct Lincoln. Booth is in a rage about a speech Lincoln just made expressing the possibility of allowing Blacks to vote. Booth changes his plans, so he is going to kill Lincoln.
Sic Semper Tyrannus! The South is avenged!
Booth entered the box where Lincoln and his guests sat. Rathbone catches Booth but not in time. As the biggest laugh line is being dropped, Booth shoots Lincoln. Lincoln immediately loses consciousness and drops to the ground.
Mary Todd Lincoln immediately drops down to comfort his husband and expose her first grievance. Rathbone turns to Booth and approaches him, Booth also with a knife with him, cuts Rathbone across the arm.
After the fight with Rathbone, Booth jumps out of the box and catches himself on the curtain with the dagger.He lands awkwardly on his leg, most likely breaking it. He is the middle of the stage. With the crowd in a fuss, Booth says "Sic Semper Tryannus (thus always to tyrants). The South is avenged!"
Lincoln, in a scene of panic, is carried out by some strong men, out the theatre, and across the street into the Peterson House. He is so tall that he had to be laid on the bed diagonally. Lincoln passed away early next morning.
Booth proceeds to run off the stage and out the back door where a horse is waiting for him. Soldiers are sent out to find him. A few days later, the soldiers find Booth in a barn, the other people with him surrender, but Booth would rather die than be caught. The soldiers sent the barn on fire. Booth was eventually shot and killed.