After the Pittsburgh synagogue attack this past October, Northeastern University criminologist Jack McDeavitt told me he feared it might herald more hate-fueled mass shootings. Last weekend, his fears came true when a white supremacist opened fire on a synagogue north of San Diego, killing one and injuring three.

Now, experts and law enforcement are struggling to figure out how to respond to the rising threat of armed extremists.

“It’s not like there is one clear right answer,” said William Braniff, the director of the National Consortium for the Study of Terrorism and Responses to Terrorism at the University of Maryland. “There are ways to find and stop attackers, but they have varying degrees of intrusiveness and protection associated with them. There are tensions here.”

When prescribing steps to prevent further bloodshed, these are the steps he and other experts are focusing on:

Increased online monitoring

The two synagogue attacks were different from past mass shootings in an important way: Not only were they explicitly ideological acts, the perpetrators of both anti-Semitic shootings were influenced by a larger white power movement. Both men posted on largely anonymous message boards and social networks like Gab and 8chan, where they were further radicalized and expressed their intention to commit the attacks. What makes the shootings particularly frightening is that the perpetrators had an audience of fellow extremists they hoped to inspire to take up arms.

Both McDeavitt and Braniff agreed that authorities need to increase efforts to monitor the online spaces where far-right extremists congregate. Law enforcement could try to identify users who clearly embrace violence and monitor them offline. Braniff warned that for such an effort to be truly comprehensive, “intelligence gathering efforts would be akin to an authoritarian state.” Still, when effectively targeted, Braniff said he thought monitoring could provide opportunities to try to intervene with people considering violence, not unlike an intervention for substance abuse.

Asking the platforms to step up

Politicians and members of the public could pressure social networks and internet hosting services to make hate speech a clear violation of terms of service, and demand consistent enforcement. This could effectively “deplatform” white supremacists, making it harder for them to exchange propaganda and exhort one another to violence.

Beyond the internet, both experts agreed that authorities and members of the public need to prevent violence-inclined extremists from getting ahold of lethal means. In the United States, that means guns. “Violent extremists are opportunists. In Middle Eastern conflict zones, extremists use IEDs because there are lots of munitions around,” Braniff said. “In contexts where firearms are available, we see more firearm attacks.”

Removing firearms before it’s too late

Background checks might make it more difficult for any extremist with a felony conviction to get a weapon, but both synagogue shooters had clean records. In such cases, an extreme risk protection order could help. The emergency gun-seizure tool, often called a red flag law, can help family members alert the police about someone who may be plotting anti-Semitic or racist violence, and the family or authorities could ask a court to promptly seize the person’s weapons.

All of these efforts depend on police and community members first acknowledging that America has a violent white power movement. “We too often dismiss these folks,” McDeavitt said. “You have to see this as a dangerous movement and not as just something crazy that will just go away.”