Ominous music plays as a man in dark clothing, sunglasses and a backpack walks towards people working in a high-rise building.
The narrator's voice warns: "It may feel like just another day at the office, but occasionally life feels more like an action movie".
Moments later, the man opens fire on a security guard near an elevator.
It's the beginning of a six-minute video created by the City of Houston in an effort to teach residents what to do during a shooting.
Local Homeland Security officials said they realised during training exercises that first responders knew how to react but citizens were far less knowledgeable.
The video emphasises a short mantra — run, hide, fight — to help people remember their options.
The video was made using US$200,000 (NZ$247,000) from a federal grant, and its release was expedited following last month's movie theatre shooting in Aurora, Colorado.
"As children we're all taught by the fire department to stop, drop and roll if you're on fire," said Richard Retz, who works for the Mayor's Office of Public Safety and Homeland Security and helped produce the video.
"Unfortunately, with our society the way it is today, we felt that there had to be a new one."
Several countries and other US cities have done educational campaigns on similar topics, including a long-running one in Israel that tells people what to do if they see an unattended package.
Such campaigns can be effective because they bring incidents people see on television closer to home, said Danny Davis, director of a homeland security graduate programme at Texas A&M University.
The overall advice in Houston's video was useful, he said, though whether a person should run or hide before attempting to fight back depends on the situation.
"You're not going to turn a civilian into a commando with a short video, but at the same time you can at least put in the back of their mind the possible options," Davis said.
"I particularly like the idea that they had in there the idea of fighting. When it comes down to it, and it's about survival, you better consider fighting."
But the video's lack of information about using a weapon in self-defence was a "glaring shortcoming", he said, noting Texas's concealed weapons law. Davis suggested the Colorado shooting, which killed 12 people, may have ended differently had someone in the theatre been armed and fired back.
Houston officials considered including a segment in the video advising armed residents to use their guns if possible. But when they delved into the facts, they got a surprise: Despite Texas' more relaxed gun laws, only about 2.7 per cent of state residents are legally armed, Retz said.
What level of training each of those gun owners has and how they would react "is an entirely different story", Retz said, adding that the city wanted to produce a video for the general population.
Following the three-day shooting rampage in Mumbai, India, that killed 166 people in 2008, Houston officials decided to use grants from the US Department of Homeland Security to train first responders to deal with a similar incident. They quickly realised first responders were well-equipped to handle such a situation but citizens were not, Retz said.
Houston used money from a US$3.6 million federal grant to research and produce the movie, said Dennis Storemski, director of the Mayor's Office of Public Safety and Homeland Security. Filming began in May and the DVDs arrived in mid-July, days before the Colorado shooting.
Initially, Houston officials planned to release the video in a well-co-ordinated safety campaign, as the city has done in the past for hurricane or flood preparedness. The shooting in Colorado, however, changed the thinking.
"The fact that the shooting was on everyone's mind, we felt that it was important to get it out there as quickly as possible," Retz said.
Since being posted on YouTube a week ago, the video has been viewed more than 220,000 times, and Retz's email has been flooded for requests to reuse the movie — from agencies across the US and as far away as England and Germany — a response he called surprising. The city also plans to distribute it in a more organises safety campaign that would reach workplaces and possibly schools.
"Visual media or video is universal," Retz said. "We wanted something that was compelling, that would draw their attention, but it was short and to the point."