Park, a 21-year-old from Northbrook, Ill., said he left the show with no regrets when he heard the bad news from host Ryan Seacrest.
Joining Park out the door was Sellers, a 27-year-old from Joliet, Ill.
"In God there is no failure," Sellers said. "So I leave here happy."
Also getting the boot were Vaughn, a 16-year-old high school student from Fort Collins, Colo., and Delamor, 22, of Miami, Fla.
"I think I was so wrapped up in trying to do everything right while being judged that I kind of lost sight of just performing," Delamor said afterward.
The two male and two female semifinalists had logged the fewest viewer votes following their on-air performances earlier this week.
The remaining 16 contestants will vie for a spot among the top dozen finalists next week.