A community college located at the heart of a deadly attack in Dallas remained closed Friday as school officials waited for police to clear the buildings. Students and staff at El Centro College hid from gunfire Thursday night and early Friday morning as a peaceful protest against police shootings was followed by a violent attack on officers.

Colleges across the country are quick to lock down if there are security concerns, especially after mass shootings such as the one at an Oregon community college last fall. El Centro College locked its doors as a precaution about 8 p.m. during the protest. About an hour later, sniper fire targeted police.

At least five officers were killed and seven others were wounded. A suspect later told police he was upset about the recent police shootings and “wanted to kill white people, especially white officers,” according to Dallas Police Chief David Brown. The suspect was killed by a police bomb robot after an hours-long standoff with police.

No El Centro students or staff members were injured, according to Ann Hatch, a spokeswoman for the Dallas County Community College District. El Centro is one of the district’s seven schools.

About 25 evening classes and several continuing education classes were underway, Hatch said; school officials don’t yet know how many students and employees were in the building during the shooting. The summer enrollment is nearly 7,500 students, most of them part time.

Video shot by Patrick Cooper, a security officer at El Centro, from inside the college is peppered with the sound of many gunshots and the shouts of authorities telling people to hide in the bathroom. Cooper did not immediately respond to messages seeking comment Friday morning.

Three El Centro buildings were damaged in the shooting, but the extent of the damage wasn’t yet known midday Friday.

Students and employees in the main building were taken to Dallas police headquarters after midnight, and two employees of the school’s Wellness Center were released from lockdown about 3 a.m. Friday.

Five campus security officers were on duty Thursday night and are working with Dallas police, according to Hatch. “Security cameras are located throughout the building. Following the shooting in Dallas last night, the security cameras went down when the college website crashed, overloaded by the volume of hits the website received. IT staff members are working to restore both the website and the security cameras,” Hatch wrote in a statement.

All classes were canceled Friday.

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An investigator points to El Centro College while working the scene of a shooting in downtown Dallas, Friday, July 8, 2016. Snipers opened fire on police officers in the heart of Dallas during protests over two recent fatal police shootings of black men. (AP Photo/LM Otero)