Rylee Goodrich, an 18-year-old who was at the movie with Barajas, was also shot and pronounced dead at the scene.
The Corona Police Department said it is working with the district attorney to add an additional count of first-degree murder against 20-year-old Joseph Jimenez, who was arrested on Tuesday evening and charged with murder and attempted murder on Friday.
Barajas, who went by @itsanthonymichael on social media, had nearly one million followers on TikTok.
Corona police Cpl. Tobias Kouroubacalis said that only six tickets were bought for the movie on Monday night and they believe Jimenez acted alone in the shooting.
"It was completely unprovoked, and the victims were shot without any kind of prior contact," Kouroubacalis said Wednesday.
Dave Goodrich, Rylee Goodrich's father, confronted Jiminez during a court appearance on Friday.
"Look at me. Look at me!" Goodrich yelled at Jiminez as several people held him back, according to FOX 11. "That was my daughter."
Theater workers found the wounded teens after the 9:35 p.m. showing of "The Forever Purge," which is the fifth installment in the series that depicts a dystopian future of America where all crime is legalized for 24 hours annually.
The Associated Press contributed to this report.