Shortly before UnitedHealth Group’s investor conference early on the morning of Dec. 4, Thompson, 50, was killed on the street outside a Hilton hotel. The suspect fled on foot, and then on an electric bike through Central Park. Authorities have yet to identify or locate the shooter, but they say the attack was targeted. 

Since then, executive security professionals have received a barrage of calls from companies and executives on edge over the news. “We’re getting calls from everybody,” Glen Kucera, president of enhanced protection services at Allied Universal, tells Fortune. “Demand for the security business follows events. If there’s a specific incident, then companies say, ‘I need to protect my executives. I need to protect my employees from this happening again.’”

Their alarm has only been compounded by new details that have emerged about the attack and speculation around possible motivations. Bullet casings at the scene had the words “deny,” “defend,” and “depose” written on them. The words echo Delay Deny Defend, the title of a book about insurance industry practices. Several internet comments about the killing have also focused on anger over UnitedHealthcare’s profits, and its record for a high percentage of patient claim denials. 

That backlash has prompted many corporate executives this week, who may have never considered security measures, to wonder if they’re really as safe as they thought. Security professionals say that clients are asking for advice about how strong their executive protection is, and if they should be doing anything differently. 

“Right about the time the news broke, I started getting calls from organizations around the country asking if I had any additional information, and then talking about what they were doing and asking, ‘Do you think we’re on the right path?’” Eric Sean Clay, president of the International Association for Healthcare Security and Safety, tells Fortune. 

Some of America’s most prominent CEOs cost millions of dollars for their companies to protect every year. Meta Platform’s Mark Zuckerberg, Tesla’s Elon Musk, and Alphabet’s Sundar Pichai all come with heavy costs for their companies when it comes to security. And although the CEOs of smaller companies cost much less to protect, corporate spending on security has increased over the past few years. 

Experts say that whether or not companies will decide to beef up their security depends on further revelations about why the shooter acted the way he did; the suspect’s reason for killing the CEO is still unknown. If the attack on Thompson was personal, then executives may be less concerned. But if Thompson’s killing was related to his role within the health care business, experts say C-suites are more likely to be willing to spend money on more safety measures for their top executives. Yet motive or no, corporate America is on edge this week as the manhunt for Thompson’s killer continues.

“Across corporate America, boards are asking the questions, CEOs are asking the questions,” Dave Komendat, former chief security officer for Boeing and founder of a risk services company, tells Fortune. “In the coming days and weeks, there will be a lot more on this topic. They’ll want to understand more about what their capabilities are. Did they need to do more? Was this an anomaly? Those are the kinds of questions that will occur.”