Djamel Agaoua, the CEO of Cheetah Ad Platform, a Paris-based advertising technology company, was Skyping with colleagues from his office in San Francisco on Friday evening, when gunshots echoed through the screen. 

Cheetah's headquarters (formerly, the company was known as Mobpartner,) are located just two buildings down from La Belle Equipe, the restaurant where 19 people were shot and killed as part of a series of terrorist attacks at six separate locations in Paris last Friday evening. The Islamic State has formally taken credit for the rampage, in which at least 129 victims were murdered.  

"La Belle Equipe is a restaurant where most of the people on the team have been more than 20 times in their life," Agaoua tells Inc. Luckily, he adds, none of his staffers were injured. 

Agaoua, who was born in Marseille, and spent most of his life in the capital city, expressed his anguish over the events on Friday -- and the fact that he wasn't physically present at the time. "It's scary," he said. "A part of you is happy that your family is not there, and part of you says you should be there with the other guys."

"It's an attack against us, against our civilization and our culture," he said.  

Amid tragedy, several companies based in Paris that landed on the inaugural Inc. 5000 Europe list for their rapid growth between 2011 and 2014, are moving forward, even as their founders candidly shared with Inc. some of the challenges that lie ahead. 

Win-Win.com, an advertising agency that has a substantial events business and is located in Paris's 18th district, and which is No. 3,745 on the European Inc. 5000, includes several staffers who lost friends and family on Friday evening.

Many killed were in the ad and marketing businesses, said Florence Mayer, Win-Win's associate general manager on the Monday after the attacks. "It was very hard for them today," she said, referring to her staffers. "But I think they managed to work because they don't want to be afraid."

Mayer added that for the moment, at least, business is slowing, as Win-Win clients are hesitant to book events in the city. "I think foreigners are afraid to come to Paris, so it's a bit difficult to explain to our clients and their [non-French workers] that it's OK. There's a lot of threat--but there's threat everywhere," Mayer said. Still, early this week, she characterized her business as "frozen." 

Cheetah Ad Platform, which has offices scattered across the globe and ranks No. 45 on Inc.'s list, typically trains all of its new recruits at the Paris headquarters. The company is finding that that will prove difficult in the coming weeks.

"Some of the people we've recruited in the last weeks are supposed to come to Paris, and they're scared," Agaoua says. "Some people will be scared to be in Paris, or to work in Paris, or to come to Paris for business."

Still, he doesn't expect that his business will take that much of a hit. "Overall, there will be some issues in the city. The restaurants and the stores will probably be impacted by this situation, but that's not our client base."

Elliott Barnes, an American founder and the chief creative officer of his eponymous design firm in Paris, also said he doesn't anticipate that business will slow. The company, which first launched in 2004, does about $2 million in annual revenue with nine employees, making the European Inc. 5000 list at No. 1,781. One project Barnes recently completed was the interior for a swanky jazz club, Duc des Lombards, with curtains cut from piano coverings. 

More to the point, he expects the city to bounce back quickly. "Parisians have this attitude, very much like a New Yorker attitude: 'You're not going to put us down, you're not going to change us, we're going to move forward,'" Barnes explained. 

Still, many business owners point out that the attacks are likely to bring about a shift in national politics, and the ultimate effect on business is difficult to predict. Marine Le Pen, the president of France's far-right National Front party, was climbing in opinion polls prior to the attacks, and analysts suggest that her numbers--and her prospects of becoming a French presidential candidate--have likely since improved. 

"The climate in France will change, because I think there is the awareness of risk," said Olivier Pelleau, the co-founder and managing partner at Turning Point, a Paris-based management consultancy. The startup works with executives both in France and the United States, with about 80 contract workers abroad, and is No. 3,969 on the European Inc. 5000. None of Pelleau's Parisian employees were injured during the attacks, but Pelleau said that many had friends who were.

Barnes agrees about the uncertain future. The attacks "will definitely affect the government, the political scene in France," he said. Whether or not that might affect the Parisian taste for luxury design--his firm's bread and butter--though, the entrepreneur is skeptical: "It's too soon to tell." (It's an inexact comparison for many reasons, but luxury spending and advertising in the U.S. declined substantially after 9/11.)

Larger companies had made a push for better internal security following the January terrorist attacks in Paris on the French satirical magazine Charlie Hebdo. Veolia, an international water, energy, and waste management service that is No. 583 on the European Inc. 5000, brought on Jean-Louis Fiamenghi in 2012 to serve as its head of compliance and security. Previously, Fiamenghi earned his chops as the chief executive at RAID (Recherche Assistance Intervention Dissuasion), the French government's anti-terrorism police force.

Fiamenghi explained that the company had already taken security measures "after Charlie," for instance by putting in place more security cameras at its water production plants, so the business could notify police immediately in the event of an intrusion. Still, he points out that modern terrorist organizations operate differently from how they did in the past, when they would attack sites of "symbolic" importance, as opposed to city streets. "After the attacks on Friday, what's happening is that we have asked to up the level of vigilance, but that simply means giving advice [to employees,]" he adds. The business has not further increased security since Friday.

Across Paris, business optimism is perhaps nowhere as apparent as it is at Cheetah Ad Platform--where one engineer, who witnessed the attacks at La Belle Equipe, returned to work on Monday, along with the rest of the company's 50 local staffers.

Of course, the attacks took a severe toll on the firm, and even Agaoua says he finds it difficult to summon the energy to focus on mobile advertising.

"I have this kind of feeling, because my name is Djamel Agaoua. My father came from Algeria in a boat. I was born and raised in this country, and I am 120 percent French. I'm happy to be, and proud to be," he said. "We have to move on. We won't change our lives for them."