Texas Gov. Greg Abbott (C) hugs El Paso resident Antonio DeAnda, 70, after a vigil ceremony at Saint Pius X Church. Photo: Joel Angel Juarez/AFP/Getty Images

"See something, say something" is going online.

The big picture: Katherine Schweit, a former FBI agent who was in charge of the active-shooter program, told Axios in a phone interview that mass shooters frequently were surrounded by people who saw danger signs in person or online.

Why it matters: FBI behavioral research has found that 80-90% of mass shooters "leaked" warning signs: "Watch out on Tuesday."

"Law enforcement is likely to be the last to hear," said Schweit, now a workplace-violence consultant.

  • "It's not uncommon when we interview people for them to say: 'He's always been like that, but he's never done anything like this before.'"

"The biggest ace in the hole we have for prevention is people listening to the people around them," she added.

  • "Employees and friends need to report concerns not because they want to get them in trouble, but because they want to help them out."

Retiring Rep. Will Hurd (R-Texas), a former CIA undercover officer, told Wolf Blitzer on CNN that threats are often "shared on social media in a way that can help tip and cue federal law enforcement":

Screenshot it.  If you're looking at it on your phone, screenshot it, and then do a search for [your] police department. There's guaranteed to be an e-mail where you can send these kinds of things and then attach that screenshot to an email and send it to local police.
You can actually find the FBI's phone number in the phonebook. I don't know if people still use phonebooks, but that is something you can go on the internet and find that as well.

Go deeper

Appeals court allows House Democrats to continue lawsuit for Don McGahn testimony

Don McGahn in an October 2018 Cabinet meeting. Photo: Chip Somodevilla/Getty Images

A D.C. appeals court on Friday allowed House Democrats to continue their case for testimony from former White House counsel Don McGahn before the House Judiciary Committee.

Why it matters, via the AP: McGahn was one of the most important witnesses in Robert Mueller's investigation. He appears on 66 pages of the Mueller report and played a central role in some of its juiciest revelations, including the fact that President Trump once asked him to fire Mueller.

There's little consensus on TikTok's specific national security threat

Illustration: Aïda Amer/Axios

TikTok has become a Rorschach test for how U.S. politicians view China, with little consensus on the specifics of its threat to homeland security.

The big picture: Much of what D.C. fears about TikTok is fear itself, and that's reflected in President Trump's executive order to ban the app by Sept. 20 if it's not sold by parent company ByteDance — alongside another focused on Chinese messaging app WeChat and its parent company Tencent.

U.S. sanctions Hong Kong leader Carrie Lam

Photo: Anthony Kwan/Getty Images)

The Treasury Department on Friday placed sanctions on Hong Kong leader Carrie Lam, following months of tension as she has allowed continued overreach by Beijing to subvert Hong Kong's autonomy.

Why it matters: It's the toughest sanction yet imposed on China for its destruction of Hong Kong’s relatively free political system.