(CNN) -- Students ducked under desks and ran for cover during a shooting at a community college in Texas on Tuesday.
Three people were injured, including a maintenance worker, in the shooting at the North Harris campus of Lone Star College in Houston, Harris County Sheriff's Maj. Armando Tello said.
Two people allegedly involved in the shooting were detained, sheriff's officials said, but no arrests had been made and no charges had been filed Tuesday afternoon. Both of them were injured, officials said.
"We haven't determined their exact involvement," Capt. Ken Melancon told reporters.
Conflicting reports emerged about the nature of the shooting.
Tello said a handgun was involved and one of the people detained had a student ID. Witnesses told CNN affiliates that at least one gunman opened fire after an altercation between two people.
Jed Young, a school spokesman, earlier said officials believe there were two shooters, and students were caught in the crossfire.
"I heard about six shots, and kids started rushing down the hallway and a few even came into our class ... They were just shouting. I couldn't hear anything," said Amanda Vasquez, a freshman who was in English class when the shooting erupted. "For me, I was just trying to get under a table, get into the back corner of the room ... and I called my mom just because I needed her to know that I was OK."
Lone Star College student Brittany Mobley told CNN affiliate KHOU that she saw the shooting.
"I saw two dudes basically get into an altercation and ... the dude that shot, he basically got angry and, you know, started shooting the other guy," she said. "A lot of people heard a lot of shots."
A fourth person at the college suffered a heart attack during the shooting, according to a federal law enforcement official who received reports from the scene.
Reports indicate the shooting occurred in an outside area between the library and the cafeteria, a law enforcement official said.
There were more than 10,000 students on the campus at the time of the shooting, Young said. The campus was evacuated and closed for the remainder of the day, according to a post on the school's website.
"I'm still hoping that all of my friends are OK," said Vasquez, who took to Twitter during the shooting to warn students away from the area. "I didn't really see any of my friends afterward. I was just trying to get to my parents."
Police and emergency responders swarmed an entrance to the campus, aerial video from KPRC showed.
Medical personnel were seen treating at least two people and moving them to ambulances. One person appeared to be handcuffed to a stretcher. Students were jogging away from some buildings, with their hands up in the air, presumably in response to police instruction.
The maintenance worker who was shot was in stable condition Wednesday afternoon, said Richard Carpenter, chancellor of the Lone Star College System.
"I heard no less than five shots, and I just ran," one student told CNN affiliate KTRK. "My heart was pounding. I was praying I wouldn't hear anymore shots. I was with a bunch of other people running and someone yelled out, 'don't push!' People were crying, I had tears in my eyes."
Another witness told KTRK he saw blood on the ground and someone shot in the leg.
"Beside him, there was one guy in handcuffs," he said.
"I just heard somebody screaming, and then after that, I heard the shots," another student told KPRC.
A spokesman for Texas Gov. Rick Perry said the governor's office was monitoring the situation.
"His thoughts and prayers are with those who have been impacted," spokesman Josh Havens said.
The Lone Star College system is the largest institution of higher education in the Houston area, and the fastest-growing community college system in Texas, according to its website.
CNN's Ed Lavandera, Brooke Baldwin, Steve Almasy, Thom Patterson, Carol Cratty, Devon Sayers, Rich Porter and Joe Sutton contributed to this report.
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