A mother who lost her son in the Sandy Hook Elementary School shooting says even though Congress is not acting, there are things everyone else can do to prevent mass shootings.

Nicole Hockley helps run Sandy Hook Promise, a gun violence prevention group. She lost her son, Dylan, in the Sandy Hook shooting.

"What was their motivation for doing this, but also the signs and signals that they gave off beforehand," she says. "That's what we teach people -- how to recognize those signs and then how to say something about it, so that action can be taken before the violence occurs."

Hockley says some of the signs are someone who cannot control their behavior, changes in mood and a fascination with guns or shootings. In the Dayton shooting, classmates say the gunman had a "hit list" of people he wanted to rape or kill and claim school officials knew about it.

She says reporting online posts is also important.

"Even if the manifestos are posted on something that a typical person might not see, they also do post things on other social media channels that are more widespread and used," Hockley says.

In prepared remarks, President Donald Trump called for a national "red flag law" similar to Connecticut's.

Hockley says even though Sandy Hook Promise and other websites have an anonymous reporting site, Congress should create a national system.