HOUSTON (AP) — A shooting on a Texas community college campus wounded three people Tuesday and sent students fleeing for safety as officials placed the campus on lockdown, officials said.

Harris County Sheriff’s Maj. Armando Tello said authorities had detained a person of interest. He did not provide any details about the people who were wounded, such as whether they were students or included the person who was arrested.

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.

Relatives identified Jody Neal, 24, as one of the people who was shot and said he was taken to Harris Health Ben Taub Hospital Emergency Center with gunshots in his arm, stomach and leg.

“He was sitting in the study room. There (were) three people on the computer and a guy walked up the stairs and opened fire on him,” Stacy Neal, Jody’s sister, told KPRC-TV. “They said it was just one guy that came in with a gun.”

Other students said they were studying or waiting for classes to start when they heard gunfire about 12:30 p.m.

“I didn’t think they were shots,” said Daniel Flores, 19. “It sounded like someone was kicking a door.”

He was in a second-floor tutoring lab with about 60 people. Once they realized the sound was gunfire, they fled to the nearby student services center, where authorities kept them for about 30 minutes before letting them go, Flores said.

Cody Harris, 20, 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 shooting comes one month after a gunman attacked an elementary school in Newtown, Conn., killing 20 children and heightening security concerns at campuses across the country. In Texas, several school districts have either implemented or are considering a plan to allow faculty to carry guns on campus. The Texas Legislature this year may also debate a bill that would allow guns on college campuses.

The Lone Star College System has an enrollment of 90,000 students and six college campuses, according to its website. Its programs in Harris County include training to be a paramedic.

Mark Zaragosa said he had just come out of an EMT class when he saw two people who were injured and stopped to help them. Officers had not yet arrived, he said.

“The two people that I took care of had just minor injuries,” Zaragosa told KHOU. “One gentleman had a gunshot to the knee and the (other) actually had an entry wound to the lower buttocks area.”

Keisha Cohn, 27, who also is studying to be a paramedic, said she was inside a building about 50 feet away from where the shots were fired. She heard “no less than five” shots and started running.

She fled to the learning center, which houses computers and study areas. Eventually, a deputy showed up and escorted people out, she said. She left her car on the campus, which was evacuated and closed for the rest of the day.

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