Thousands volunteer, donate to help Mike Bloomberg and Everytown fight gun violence

Former New York City Mayor Michael Bloomberg
Stephane Mahe | Reuters
Former New York City Mayor Michael Bloomberg

Within 24 hours of the mass shooting at Marjory Stoneman Douglas High School in Florida, Everytown for Gun Safety, a nonprofit organization backed by billionaire and former New York City mayor Mike Bloomberg, received $750,000 in online donations.

The day after the incident, Bloomberg, a long-time advocate for tighter firearm regulations, urged citizens to take action and "demand common-sense solutions to the gun violence crisis."

After the mass shooting at a country music concert in Las Vegas in October, which left 59 dead and over 500 injured, the former mayor took to Twitter to announce that he would match all donations to Everytown.

"US has a gun violence problem," he wrote. "I'll match every donation. Give now."

Everytown tells CNBC Make It that 75,000 people have also reached out to volunteer just in the past week. A representative did not specify whether Bloomberg is still matching donations.

The group tracks school shootings and, after some criticism of its methodology, recently revised its tally for this year from 18 down to 17. It has also launched a "five-action plan" for citizens who want to make a difference, which involves pledging to vote, researching which politicians accept NRA donations, registering friends to vote, holding leaders accountable and running for office to champion the cause of sensible gun laws in your community.

When the NRA introduced a bill last year to legalize concealed-carry reciprocity, which would allow gun owners to carry weapons freely between states, the billionaire said he would spend $25 million to fight it, Politico reports. The bill has since made its way through the House of Representatives but is expected to face an uphill battle in the Senate.

As Everytown notes on its site, "Every day, 96 Americans are killed by gun violence." When a version of this article was previously published in October, that number was 93.

"Americans are 25 times more likely to be murdered with a gun than people in other developed countries," the site says. It also highlights the effects of lenient gun laws on issues like domestic violence and suicide.

Donations go toward increasing regulations in an effort to reduce gun crime.

Mass shootings are typically followed by a surge in donations on both sides of the gun control debate. In the months following the Sandy Hook Elementary School shooting in 2012, the NRA raised 350 percent more than it had in the same period the previous year. Advocates for tighter gun control raised money and took action, too, but, according to PBS, "the gun-rights lobby outspent, out-organized and out-maneuvered gun-control advocates at both the state and federal level."

In result, "states passed more than twice as many laws expanding gun owners' rights than they did gun-control measures."

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This is an updated version of a previously published article.