Ford starts to see the hosts the way Arnold did, and brings Wyatt back to life
Though all of this happened in the past, we don't learn it until the very end of Season 1. Until that point, our knowledge of Wyatt came from Teddy (James Marsden), a host and love interest to Dolores. Teddy had memories of Wyatt shooting up Escalante, but remembered him as a bearded man in uniform. He saw Wyatt as a ruthless, cult-like demigod, who believed the park belonged to him, and who spouted philosophies that got the attention of other hosts.
But Teddy's memories aren't fully his own; he was programmed by Ford to see these events unreliably. In reality, Teddy was present when Dolores shot up Escalante, and helped her with the massacre. Like Dolores, Arnold used Teddy to carry out his own vendetta against Ford and the park. And now, Ford has disarmed his ability to remember those events.
That's because Ford had his own Arnold-like revelation, and throughout Season 1 was planning his own elaborate suicide; like Arnold's, but on a larger scale. He dug up Escalante, which was buried after the massacre, and worked on a new narrative for the park called "Journey Into Night," which he was to present to his board. When that night came, in the Season 1 finale "The Bicameral Mind," Ford addressed the audience, telling them they abuse the hosts for their own self interest, and that they are a part of his new narrative. He then says the same phrase Arnold used -- "these violent delights have violent ends" -- which instructs Dolores to shoot and kill him. She does, and then opens fire on the rest of the crowd, as Teddy and Bernard (a host duplicate of Arnold) watch in horror.