By Elizabeth Warren

A month ago, we launched YouFundGuns.com – a project to urge some of the country’s largest shareholders in gun companies to push them for responsible behavior.

We have good news: This project is starting to get attention – and results.

BlackRock – the world’s largest shadow bank – announced a few weeks ago that it will offer new investment fund and pension plan products and that exclude companies that manufacture or sell guns.

Don’t get me wrong – this is only one small step. BlackRock and the other investment firms can (and should) do a lot more to pressure gun manufacturers and retailers.

But think about it this way: If investors in your hometown and all over the country opt-out of funding not only gun companies, but also gun retailers like Walmart – and if they feel the financial impact of people demanding gun reform – we have a fighting chance to influence real change.

The Parkland student leaders are also jumping into this fight. Earlier this week, David Hogg tweeted:

This team is making a real difference by speaking out and making your voices heard. But BlackRock is only one firm, and the others are laying low, maybe hoping all this attention will blow over. But we’re not going away.

On this National Walkout Day, will you call or tweet to the country’s biggest investment firms and urge them to show some political courage to stand up to the gun industry?

A few weeks ago, I stopped by an amazing #TownHallforOurLives organized by local students and Stop Handgun Violence volunteers in Natick, Massachusetts.

These smart, passionate young people made it very clear: they’re not going to fighting until we get the change we need to keep kids safe in their classrooms and on our streets. They aren’t giving up – and neither can we.

I’m going to keep fighting my heart out in Washington until we pass common-sense gun reform. But every change is important – and urging shareholders to use their financial muscle so that gun manufacturers and retailers they fund will regulate their own weapons is another tool in our toolbox.

This team has already helped get results with BlackRock – now let’s keep them coming. Go to YouFundGuns.com to call or tweet at the investment firms that make money off of gun sales.