Neighbours comfort a man who was prevented from returning to his home at the scene of the investigation around the area of the SUV vehicle where two suspects were shot by police following a mass shooting in San Bernardino, California December 3, 2015. (Mike Blake/Reuters)

Was the San Bernardino shooting an act of terrorism or workplace rage? It doesn’t really matter, in terms of the need for better regulation of assault rifles and semiautomatic weapons.

The growing evidence that this latest attack was terrorism should galvanize a citizens movement to demand better protection against such mass shootings, whether they’re the work of Muslim extremists, enraged antiabortion militants or mentally unstable loners.

Enough is enough,” said President Obama immediately after the shooting in Colorado Springs last week. This conviction should only deepen as the investigators try to determine the motivations of the suspected shooters in San Bernardino, Syed Rizwan Farook and Tashfeen Malik.

The attackers certainly intended to terrorize. They were wearing combat gear and armed with two AR-15 semiautomatic rifles, two semiautomatic pistols and what police say were more than 1,600 rounds of ammunition. Three pipe bombs were found at the attack site, and 12 more pipe bombs were found at a residence nearby.

Were the shooters “terrorists”? News reports focused on the couple’s Pakistani backgrounds, his trip to Saudi Arabia to meet and marry her, and his online contacts with extremists. The FBI is investigating the case, including the puzzle of why the couple targeted a holiday party at a social services center — not an obvious jihadist magnet.

After the mass shooting in San Bernardino, Calif., on Wednesday that left 14 people dead, details are starting to emerge about the two shooters. Here's what we know about Syed Farook and Tashfeen Malik. (The Washington Post)

But how did the attackers get all those weapons? That’s an urgent question, no matter what their motivations were. Conservatives who are worried about terrorism and liberals who focus on gun safety should agree that access to such assault weapons is a deadly threat in the United States.

The horrifying events in San Bernardino, Calif., should be a unifying moment in the gun debate, rather than a polarizing one. Left or right, blue state or red, Americans ought to agree that Farook and Malik shouldn’t have been able to obtain the types of weapons that killed so many people on Wednesday. Regulations that might reduce the likelihood of another San Bernardino could also contain the violence that killed three people last week at a Planned Parenthood clinic in Colorado, and 10 at a community college in Oregon in October, and nine at a church in South Carolina in June, and the still gut-wrenching Connecticut school massacre that killed 28 three years ago.

President Obama made the connection between fighting terrorism and gun safety in an interview with CBS News on Wednesday night. “For those who are concerned about terrorism, some may be aware of the fact that we have a no-fly list where people can’t get on planes. But those same people who we don’t allow to fly could go into a store right now in the United States and buy a firearm — and there’s nothing we can do to stop them. That’s a law that needs to be changed.”

Politicians need to rethink their reflexive invocations of the Second Amendment, and the idea that the gun lobby is too powerful to challenge. Governors who want to protect their citizens from terrorism should focus less on blocking immigrants from Syria and more on limiting a potential terrorist’s ability to purchase assault weapons and explosives. Congress should think about having a “no-buy” list for semiautomatic rifles that’s equivalent to the no-fly list. State and local legislators should look for ways to screen potential shooters — with new background checks and permit requirements.

The Second Amendment may not be an impermeable barrier to gun safety, either. In his recent book on the Constitution, “American Epic,” Garrett Epps, a law professor at the University of Baltimore, dissects the amendment’s puzzling language: “A well regulated militia being necessary to the security of a free State, the right of the People to keep and bear arms shall not be infringed.” He argues that James Madison and the other framers were focused largely on assuring the states that they could maintain their own militias even as a federal standing army was created, rather than on individuals’ gun ownership rights.

The Supreme Court has allowed room to restrict guns, argues Adam Winkler, a constitutional scholar at the University of California at Los Angeles. He notes that the justices “left many large, important questions unanswered” in their narrow, 5-to-4 decision rejecting a local handgun ban in the 2008 case District of Columbia v. Heller . “Since Heller, the lower courts have upheld the overwhelming majority of gun laws,” he explains. “Heller doesn’t have to be narrowed for us to do more to reduce gun violence.”

Those who plot mass violence shouldn’t be able to obtain semiautomatic weapons so easily, whether we define these people as terrorists or not. That’s one clear lesson of San Bernardino.

Read more from David Ignatius’s archive, follow him on Twitter or subscribe to his updates on Facebook.