Houston County Sheriff Ed Gonzalez told media sources that the students and faculty member were killed at Santa Fe High School, which went on lockdown around 8 a.m. Ten people were wounded.
Federal authorities have confirmed the identity of the captured shooter as Dimitrios Pagourtzis, CNN reports.
Pagourtzis, who used both a shotgun and a .38 revolver during the shooting spree, wanted to end his own life, Gov. Greg Abbott said during a press conference. Authorities also found explosive devices at the school and off campus, which appear to have been made by the shooter, he said.
"[The] shooter has information contained in journals on his computer and his cell phone, that he said that not only did he want to commit the shooting, but he wanted to commit suicide after the shooting," Abbott said.
Two school district police officers were on campus at the time the incident began and moved to apprehend the suspect, according to Abbott.
Police are questioning two additional people in connection with the shooting, Abbott confirmed.
