One of the biggest challenges for emergency responders would be the chaos created on campus by a gunman on the loose.
"Somebody's trying to get you, somebody's really trying to hurt you -- that really creates the hysteria," said L.A. City Fire Capt. Carlos Calvillo.
From controlling the fear, to rescuing the injured, to tracking down the suspect -- the large-scale scenario tested every level of response. More than 300 law enforcement and medical personnel took part in the massive, multi-agency drill.
"You want to train the way that you're actually going to operate in the field," said LAPD Officer Julianna Sohn. "So, you want to make it as real as possible and create a scenario that we can actually test for capabilities."
Students and staff said they appreciate the university being proactive, ready for a terrifying but all-too-realistic scenario.
"It makes me feel safer knowing that they're preparing for this in any scenario," said UCLA student Andriana Trang.
"I'm happy to know that in case something ever does happen like this that, as students, we have the assurance that we're going to be safe in this situation," said UCLA student Kyle Babbitt.