(CNN) -- If a shooter came into some of the biggest classrooms at the University of California-Berkeley, recent graduate Scott Alto wonders whether students would be able to protect themselves.
A memorial created by students at Northern Illinois University honors those killed in the shooting.
Alto said some of the big lecture room doors don't have locks and others open out to the hallway on the Berkeley campus, something he thinks leaves students on campus vulnerable to an attack.
"Students at Virginia Tech said they barricaded themselves with their bodies," Alto said. "In some of these rooms at Berkeley, that just wouldn't be possible."
After the shooting at Northern Illinois University last week, students on campuses across the country are wondering whether they are safe.
Some students say they want the administration to install security features such as extra cameras and metal detectors. Others are calling on them to fix broken blue emergency lights. Watch a Kent State student talk about security »
Some students, professors and campus police officers argue a person determined to kill cannot be stopped, but say they are doing everything they can to put a proper security system in place.
The following is a sample of e-mails sent from CNN.com readers, some of which have been edited for length or clarity:
Liann Casey of Miami, Florida, Florida International University
Although my school's campus has its own police, I hardly see them and I feel like there is no quick way to access them in an emergency situation. At my old school, University of Miami, they have "blue light" poles distributed all throughout the campus with emergency phones directly linked to the campus police. They claim that the police will be there within minutes of your call. At orientations and events, the campus police regularly set up a table to promote campus safety and gave away pens with emergency numbers on them. Help never seemed far away. My current school, Florida International University, does not yet have any of these safety implementations and my nerves suffer for it.
Scott Alto of Berkeley, California, University of California, Berkeley
I am a recent graduate of the University of California, Berkeley. If a shooter were to come on campus there are very few classrooms with inside locking doors.
Our instruction system requires so many different instructors bouncing around to different classrooms that the campus cannot issue keys to them. This means they cannot lock doors in a situation that should result in a lockdown. Many doors open out into the hallway, preventing any chance of blocking a door with furniture if a shooter were to come onto campus.
Bryan Hernandez of Champaign, Illinois, University of Illinois Champaign-Urbana
I work for the University of Illinois Champaign-Urbana police department as a Student Patrol Officer. I see first hand that the men and women there are outstanding officers who show me respect and professionalism when it comes to their jobs. They are constantly training for situations involving school buildings where shooters might be located, and always have a presence on campus. Officers are even stationed in the Union on weekends to ensure the safety of those leaving late or enjoying a quiet night.
Brandon Ackerman of Boca Raton, Florida, Lynn University
I go to a small private college in Boca Raton, Florida, and I feel campus safety is a No. 1 concern for students these days. Our school instituted a program for students who feel if their peers or fellow classmates are showing any behavior that is out of the ordinary or seem depressed or not acting like themselves, they can be reported anonymously to campus safety and the school will seek counseling sessions for them.
Alex Franks of Cheney, Washington, Eastern Washington University
I attend Eastern Washington University, where our campus police take good care of us. They have put in place an e-mail/SMS (text messaging) system to alert students instantly if anything is amiss. Family of students can also sign up for the service to be informed as well. I feel incredibly safe on campus because of this system -- I think this is the only practical way to keep in touch with students during our busy days, and I can only hope we will never have to use it beyond announcing snow days.
Elizabeth Fitzgerald of Boulder, Colorado, University of Colorado-Boulder
The whole "blue light" system is a joke here. Blue lights with buttons on them to dispense the authorities to the area are "strategically" planted around campus for students to utilize in an emergency. The locations are insane. Most of the time they are in a place in which an attack would probably never happen because it is off a major campus road or by major dorms ... places where there are always people at all hours of the night. In the legitimate "dark corners" of campus, you find a blue light once in a blue moon. It's better than nothing ... but it's such a weak attempt at security.
Laura Antonuccio of Lincoln, Nebraska, University of Nebraska-Lincoln
Our university recently put an emergency alert system into effect that provides students with the option of receiving texts, phone calls, e-mails, faxes, etc. in the event of an emergency; this is definitely a step in the right direction toward helping students feel secure.
There are also several preventive measures that schools and communities can implement; for example, setting up anonymous tip lines for individuals to call if they fear someone they know may be planning something of this nature.
Joseph Riedel of Washington, American University
I attend American University in Washington, D.C. I generally feel pretty safe on our campus. Our school has taken some pretty aggressive measures in recent years, such as installing emergency call boxes around campus, live monitoring surveillance cameras in parking lots, and frequent security checks around campus at night.
After Virginia Tech, our university also revamped and added emergency strategies, such as text messages in cases of emergency, quick lockdown procedures, and increased security at the front desks of all dormitories. E-mail to a friend
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