"He came running and swinging at my neck, as I tried to get out of the way," she said.
Garcia said buildings still were being searched Tuesday afternoon. Long lines of vehicles carrying students and staff streamed off campus as law enforcement directed traffic away from the school.
Student Teaundrae Perryman said he was in class when he received a text message from a friend and went outside to see a young woman being loaded into an ambulance with what appeared to be stab wounds to either her neck or head. He said he didn't receive an email alert from the college until 11:56 a.m.
"I was concerned but I wasn't afraid because I was with a large group of people," the 21-year-old said, later adding, "The police got to the scene very quickly."
The four people taken by helicopter and two others with moderate injuries were taken to Memorial Hermann Hospital. Of those six, two patients remained in critical condition, three have been upgraded to good condition and one was discharged Tuesday afternoon, hospital spokeswoman Alex Rodriguez said.
One student said she learned one of her classmates was stabbed after leaving the school's Health Science Center building.
"I called to check on another classmate who was still inside the building and she said the classroom was on lockdown and she said one of the classmates had been stabbed," said Margo Shimfarr-Evans told KHOU-TV. "It happened in the hallway."
Courtland Sedlachek, 18, was in class when his phone started buzzing along with the phones of everyone else in class. The room was temporarily locked down, but students were let out and off campus a short time later, in what Sedlachek described as an orderly evacuation.
He described his reaction as a "little bit of nervousness."
The attack came three months after a different Lone Star campus was the site of a shooting in which two people were hurt. The suspected gunman in that incident is charged with aggravated assault.