When a shooter opened fire on YouTube's campus before killing herself, Silicon Valley didn't just experience a tragedy that's rocked other communities and prompted an intense debate over gun control in the United States. The incident may have also prompted a rethink among tech companies who've enjoyed a culture that's embraced open spaces, including cafes, restaurants and gift shops, that are shared with the public.

While there have been a few incidents involving gun violence at a tech company, they are rare. Two years ago, an Apple engineer reportedly committed suicide by shooting himself in a conference room at the company's Cupertino, California, headquarters. In 1988, a fired engineer at ESL Incorporated, a software design and hardware company, killed seven people and injured four at its offices in Sunnyvale, California.

"You can bet every head of security in Silicon Valley is meeting with [their teams] today," said Paul Saffo, a longtime technology forecaster for the industry. "They're asking, what are the lessons learned and what to do they need to rethink?"

The shooting on Tuesday in San Bruno, California, a 15-minute drive south of San Francisco, left three people hospitalized and employees of the Google-owned video site traumatized. YouTube's Silicon Valley neighbors were quick to speak up, with Apple CEO Tim Cook, Uber CEO Dara Khosrowshahi, Amazon CEO Jeff Bezos and Twitter Chief Jack Dorsey tweeting out their sympathy and support.

"I can't imagine what our friends at YouTube are feeling and dealing with right now. We're here for you and your families and friends," Dorsey said, before noting that Twitter was tracking people on its platform spreading misinformation about the shooting. Dorsey also called on President Donald Trump to adopt policies enforcing universal background checks on weapon purchases and funding research into gun violence prevention and intervention programs. "We can't keep being reactive to this, thinking and praying it won't happen again at our schools, jobs, or our community spots. It's beyond time to evolve our policies."

At a press conference on Wednesday providing more details about the shooting, San Bruno Police Chief Ed Barberini touched on security at tech campuses. 

"We're always advocating heightening security and we always want to strengthen security measures," Barberini said. "We're always looking for opportunities to harden targets or make environments as safe as possible for for folks that work there."

Silicon Valley -- the place, not the state of mind -- sprawls 50 miles between San Francisco and San Jose. Many of the companies in the area are nestled on the quiet peninsula of the San Francisco Bay, amongst quiet communities and suburbs. Still, their offices attract tourists the world over, who come to pay homage to some of their favorite tech brands, like Google and Apple.

Google has a sprawling campus in the heart of Silicon Valley that draws visitors who can walk between buildings, sit outside in park-like spaces and gawk as employees ride multi-colored company bikes. The company didn't initially have anything specific to share about its security plans. Instead it, pointed to a tweet by CEO Sundar Pichai, who responded to the shooting: "Over the coming days, we will continue to provide support to help everyone in our Google family heal from this unimaginable tragedy."

But in a statement Wednesday, the company said it will up security at its offices. "We are revisiting this incident in detail and will be increasing the security we have at all of our office worldwide to make them more secure not only in the near term, but long-term."

Facebook is headquartered in Menlo Park, California, on a campus that's closed off from the public. But tourists often take selfies with the huge "Like" sign with a thumbs up at the entrance to its headquarters. The social network also declined to share details about specific security protocols. But a spokesman said, "The safety of our employees is paramount, and we work hard every day to maintain a safe and secure environment for our community."  

Apple built a standalone visitor center where guests check in before being allowed onto its new 175-acre circular Apple Park campus in Cupertino. Across from the center, it's set up a store and a new cafe. The company declined to comment. 

Twitter, which is headquartered in a high-rise in San Francisco that has its own full-service cafeteria for employees so they don't have to venture out for meals, said it had no specific details to share. But the company noted it does have corporate security protocols and a security team in place. 

"I think this is going to make people rethink the open nature of campuses in Silicon Valley," internet entrepreneur Jason Calacanis said in an interview with CNBC. "We have a very open culture here. People can walk up to almost any building and I think this could be a moment to reconsider -- like schools are having to reconsider, sadly -- having open campuses and putting fences around them and having double layers of security."

The other issue the tech industry needs to reckon with is making sure it's prepared for emergency situations. 

After the shooting at Marjory Stoneman Douglas High School in Parkland, Florida, in February, there was a push for schools to practice more active shooter drills to prepare students for those situations. Now that tech companies have been confronted with the reality that a mass shooting can occur on their campuses, the question is what plans they have to prepare for the worst.

According to Ready.gov, a website by the Department of Homeland Security that tries to prepare people for emergency situations, the best thing to do in the event of an active shooter is "run, hide or fight." Run away from the shooter, leave your belongings, and help others escape if possible. If you can't escape, hide and silence your devices so they won't vibrate. And if none of that is possible, fight the shooter as a last resort, the website says.

We reached out to several other big tech companies about their security protocols. Microsoft, Salesforce, Mozilla, Slack and Oracle declined to comment. 

Saffo said the biggest companies in the Valley are already practicing those drills, but the shooting at YouTube should bring safety to the forefront. "Everyone in Silicon Valley right now is in mild shock," he said. "It's waking people up."

CNET's Dara Kerr, Sean Hollister and Laura Hautala contributed to this report. 

Update, 5:01 p.m. PT: Adds statement from Google on increased security at its offices. 

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