LOS ANGELES (AP) — When an active shooter alert spread across the UCLA campus Wednesday, some students found themselves in a frightening predicament: They were told to go into lockdown but couldn't lock their classroom doors.
Images of students piling tables, chairs and printers against doors on social media sparked alarm and raised questions — yet it was hardly the first time students at a university or school were unable to lock their doors during a shooting.
The same issue arose during other recent deadly attacks, including one at Virginia Tech in 2007 where students barricaded themselves inside rooms and at Sandy Hook Elementary shooting in 2012 where teachers did the same.
Some schools have installed locks in recent years following attacks, but experts say wider adoption has been hindered by the cost to retrofit doors and local fire codes that require doors to open in one motion during emergencies.
Yet once an active shooter is in a building, most security experts agree getting into a locked room is one of the most effective deterrents against getting injured or shot.
"How many deaths would it have taken for us to address this issue more seriously?" said Jesus Villahermosa, president of Crisis Reality Training, noting that an assailant, knowing police are on the way, usually won't bother trying to access a locked room.
The former deputy sheriff said UCLA was fortunate in that shooter Mainak Sarkar targeted professor William Klug and then committed suicide. If he'd gone on a rampage, he might have easily found students unable to defend themselves.
The university said Friday it was "assessing safety measures" across the campus and will make appropriate changes.
It's unknown exactly how many school and university classrooms don't have doors that can lock from the inside. Villahermosa said the issue is more prevalent on college campuses than K-12 schools.
There are a variety of reasons why a school may not have classroom locks.
Older buildings constructed at a time when classrooms typically contained just desks and a chalkboard — and not the expensive technology many have today — frequently did not include them.
Fire safety regulations for rooms with 50 or more students typically require that doors swing outward and be opened in one motion, meaning a bolt that has to be turned first would be a violation.
Others worry locking doors from the inside in itself could pose a threat. If an attacker walked inside and locked the door, students would be trapped. And the cost of installing new doors and locks can stretch into the millions.
Even when there is a lock, the shooter has often been a student with access to the classroom or building.
"We should be spending more time on prevention than door locks," said Dewey Cornell, a forensic clinical psychologist at the University of Virginia.
The National Fire Protection Association's life safety code adopted in 38 states does not prohibit putting locks on doors, division manager Robert Solomon said. But there are certain types of locks schools must install.
Solomon said the types of locks found in many hotel rooms are an effective example. The door can be bolted from the inside but it opens in one motion when the handle is turned. Locks like those can cost up to $500 to install.
The price rises when the entire door has to be replaced, he said.
"Schools usually don't have a lot of extra capital money sitting around," he said. "But it's something that they're thinking about now."
After previous shootings, some universities have enacted some measures.
Lawmakers in Oregon recently approved $6 million for improvements at Umpqua Community College, including installing additional locks. In 2015, a 26-year-old man shot and killed nine people at the school.
This year, the University of Connecticut announced it was installing new locks on classroom doors. Purdue University, where a student killed one person in a classroom shooting in 2014, has installed locks for all classrooms, a spokeswoman said.
Students and faculty complained about not being able to look doors in both the Purdue and Umpqua shootings.
California State University Fullerton has also started installation of classroom locks.
"If we're asking students and our faculty to shelter in place," CSU Fullerton Police Department Capt. John Brockie said, "we feel that it's important to give them the tools to effectively do that."
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