Are mass shootings preventable? These countries have tried

One-third to half of those killed by police are disabled, a recent report says. “Our problem isn’t with police,” one mental health advocate says, but both sides say officers need more training.

Portugal has gone perhaps the farthest in decriminalizing drug use. It hasn't stopped drug usage, but it has reduced deaths, the spread of H.I.V., drug crime, and imprisonment.

Across the country, hospitals are embracing intensive intervention programs to help victims of violence — including those who have criminal histories — after they have been brought in for treatment of injuries. Such programs can help prevent retaliation, reduce the chance a patient will be violently injured again, and put people on track for success.

The Centre for the Prevention of Radicalization Leading to Violence in Quebec has expanded rapidly, becoming a model for programs around the world. What sets it apart from projects in Europe and the United States is that it confronts extremism of all stripes — not just Islamist — and focuses on behavior that signals the risk of violence, not just radical ideas, only involving law enforcement as a last resort.

Many young Latina women live their lives in fear of gang violence. The Montgomery County Street Outreach Network rescues girls in danger and offers services to them in order to help them change their chances of success.

In Mancos, Colorado, the school board voted “no” to arming school staff in the traditionally Western town. Across the United States, the question of arming teachers is being brought up as a response to the increase in school shootings. The policy is highly contested, with some saying it provides students with a feeling of safety, but others saying the risks associated are too high. For the Mancos community, such a vote is a surprise given the town’s gun-friendly history, but is explained by the increase in new residents.

Crime-tracking mobile apps give millions of Brazilians crowdsourced data on urban violence, alerting people to dangerous places and filling gaps in government data on shootings, robberies, and other risks. But apps such as Fogo Cruzado (“Crossfire”) and Onde Tem Tiroteio (“Where There's a Shooting”) offer statistically crude glimpses of crime, distorted by media and racial biases that one expert blames for myths about the risks people actually face.

Mr. Dad’s Father’s Club mentors local youth to nurture their social and emotional well-being, making them better equipped to handle the world around them. The Club also provides mentorships for fathers, helping them learn how to be more present in their children’s lives as research indicates the presence of positive role models can make youth more resilient when exposed to violent or negative environments. There are currently over 150 fathers who volunteer for events with the Club.

The Institute for Nonviolence Chicago is working to reduce gun violence by reaching out to victims and perpetrators immediately after the violence. The organization negotiates peace and offers cognitive behavioral intervention services to help them develop strategies to keep negative emotions from turning into violent actions.

Durham, North Carolina, instated an alternative crisis response program that dispatches social workers to respond to 911 calls about people in mental health crises. The team’s successes earned the support of an initially skeptical police department.