HOUSTON -- Authorities say the shooting at a Texas community college was the result of an altercation between two people, and at least one was a student.

Harris County Sheriff's Maj. Armando Tello says a college maintenance man was injured in the crossfire. He says another person was taken to a hospital for medical reasons.

Tello says officers were called to the Lone Star College System campus about 20 miles north of downtown Houston before 1 p.m. Tuesday.

The incident at first prompted students to barricade themselves in their classroom, and then sent them fleeing for safety as officials placed the campus on lockdown.

Tello said authorities had detained a person of interest.

Authorities thought there could be a second shooter, according to a law enforcement official in Washington who spoke on condition of anonymity because he was not authorized to discuss the ongoing case.

The school's official Twitter feed said the shooting was between two people and that the situation was under control. It had issued an alert on its website earlier, telling students and faculty to take immediate shelter or avoid the campus.

Aerial footage from local television stations showed police cars and ambulances parked on the Lone Star College System campus about 20 miles north of downtown Houston. Emergency personnel could be seen tending to people on stretchers, while others ran from a building led by officers.

Mark Smith, spokesman for the Harris County Emergency Corps, said four people were taken to two hospitals. He said at least two had gunshot wounds, and one appeared to have had a heart attack related to the shooting. He said one was in critical condition.

Cody Harris, 20, he said he was in a classroom with about six or seven other students waiting for a psychology class to start when he heard eight shots. He and other students looked at each other, said "I guess we should get out of here," and fled.

"I was just worried about getting out," Harris said. "I called my grandmother and asked her to pick me up."

The Lone Star College System has an enrollment of 90,000 students and six college campuses, according to its website.

Along with the college, four nearby schools in the Aldine Independent School District went into lockdown, a district spokesman said.

Lone Star student Daniel Flores, 19, said he was in a tutoring lab on the second floor doing homework when he heard six to seven shots.

"I didn't think they were shots," he said. "It sounded like someone was kicking a door."

About 60 people were in the lab, and they began running out of the room once they realized the sound was gunfire, he said. They fled to a nearby student services center, where authorities kept them there for about 30 minutes before letting them go.

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Associated Press writer Eileen Sullivan contributed to this report from Washington.