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The two sessions took place on the Merced College campus on Friday.
"It's unpredictable. You don't know when or where those things are going to happen, and you want to be ready for it," Merced College Police Chief Matt Williams said.
Williams said the sessions were planned several months before Friday's tragedy. However, many said the incident in Texas was the reason they came to the class.
"When I saw the news, I decided it's now or never," Merced College employee Vanessa Cruz said.
Williams advises people to be prepared, and leave the area immediately if the shooter is far enough away. If running away isn't an option, hide if you're not able to escape.
"Run as fast as you can, far away as you can from where you hear the pandemonium. Don't get in your car and drive because you're going to create a traffic jam for first responders," Williams said.
Being an open campus, Merced College faces more of a challenge. Along with adding more officers, campus officials say they're making some other improvements to keep the people safe.
"One of the things we're in the process of doing now is changing out several of our door locks to make them lockable from the inside. We're in our first phase right now. We're looking at tinting windows. That's another we've already started and initiated," Vice President of Administrative Services Joseph Allison said.
Allison said there are about 15,000 students and 1,000 staff members on the campus.
Officers also advise people not to assume that others have called 911, and to do so when you've run far away from the scene.