This time the campus attacker didn’t have a gun—he had a knife.

Still, the scene at Texas’s Lone Star College on Tuesday was all too familiar: police in riot gear, fleeing students. The difference between this and so many other recent school shootings is that so far no one has died, because the attacker, suspected to be a 21-year-old student, used a knife in his spree rather than a handgun.

“It was a chaotic scene,” said Capt. Robert Rasa of the Cy-Fair Volunteer Fire Department. Rasa said 15 people were injured in the attack, and four of them are in critical condition. The victims were found scattered on two floors each of two of the campus’s health-science buildings, he said. “All the injuries we treated were consistent with laceration-type injuries,” said Rasa. “Most of the injuries were in the head and neck area. Most of the victims were in the hallways transitioning between classrooms.”

Others victims, he said, came to the emergency workers themselves. “We had some walking wounded come to us.” Some eight ambulances and two helicopters were used to transport the victims to area hospitals. Rasa added: “As far as I can tell most of the victims were students.”

Asked why the suspect would use a knife, Rasa had no explanation. “These days it could be anything," he said. "You just never know what is going through someone’s mind.”

The college, which serves about 19,000 students, was still under lockdown as of late afternoon.

At a press conference, Harris County Sheriff Adrian Garcia would not release the suspect’s name or a motive for the attack. “Technically the campus is a crime scene,” said Garcia, who was flanked by dozens of officers and college officials. “Let us get the facts straight. It is a fluid scene.”

Garcia said his department is “still collecting evidence.” Despite eyewitness reports that a knife was used in the attack, Garcia would not confirm the type of weapon or if a weapon had been found.

"We do not know exactly what type of weapon was used other than to say that it is at this point an unknown instrument," he said. "We don't know whether a knife or some other type of instrument."

The rampage began shortly after 11 a.m. at the Cy-Fair campus of the Lone Star College’s Health Science Center in Cypress, Texas. Students were seen fleeing the campus as police began to search for the suspect. Police swarmed around two of the nearby buildings and began searching vehicles as students and teachers attempted to drive off the campus.

At first police and college officials thought that two armed suspects were on the loose, and students were warned to stay away from the area and seek shelter in a safe location. Lone Star’s Twitter feed told students to “Seek Shelter Now,” and “If away, stay away.”

Shortly after that, the student alert changed to “male on the loose stabbing people,” said Garcia. “That is what we had to work with.”

A suspect was arrested within 15 minutes of the alleged attacks. One student told a local news source that he helped tackle the man as he ran out of a building and described the suspect as having a hearing impairment. The suspect, he said, was dressed in black and armed with what appeared to be an X-Acto knife. After he was wrestled to the ground, the suspect reportedly said, “I give up, I give up.”

Garcia would not comment about the details of the arrest, but said the suspect was apprehended “not by his own choice.”

Student Michelle Alvarez told the Houston Chronicle that the suspect swiped her neck as he ran past her. The newspaper reported that she had a small red line of blood running down her neck. “He came running and swinging at my neck as I tried to get out of the way,” she told the paper.

Another student told the Chronicle that he saw a victim with her mouth slashed open.

The Cy-Fair campus is one of six that make up the Lone Star College System. In January three students were wounded in a shooting at the college’s North Harris campus. The shooter, Trey Foster, is awaiting trial.