Quick Lockdown After College Shooting

He said he was impressed by how quickly the school responded. "That's one of the mistakes Virginia Tech made -- they didn't lock down campus," he said.

In the months since that attack, which brought harsh criticism to Virginia Tech's administration for not warning students that a gunman was at large, many college administrators added crisis alert systems.

Schools revamped Web sites, added security officers and updated emergency plans made after the Sept. 11 attacks.

Students at George Mason, Georgetown, George Washington and Catholic universities and at the University of Maryland, among other schools, can sign up for cellphone text-message alerts. Some schools, such as Georgetown and American, have held simulated campus shootings with city police officers.

Delaware State officials said they used "multiple redundancies" to notify people, but they did not send either text messages or e-mails to all students, which some students said would have been the quickest way to notify everyone.

"We can't assume people are going to read their e-mails at 1 a.m.," Sessoms said. "We went around and knocked on doors."

Staff writers Theola Labb¿, Sylvia Moreno and Jonathan Mummolo and staff researcher Meg Smith contributed to this report from Washington.