Monday night, a gunman wearing a bulletproof vest killed five people in a southwest Philadelphia neighborhood. Two children — ages 2 and 13 — were injured.

Another shooting occurred the same night at a street festival in Fort Worth, Texas, killing three people and wounding eight.

One day earlier, in Baltimore's Brooklyn Homes neighborhood, a shooting at a block party killed two people and left 28 injured.

These are among the 11 mass shootings — defined as acts of gun violence injuring or killing at least four people — that have occurred this month, and 346 mass shootings since the beginning of the year, according to the Gun Violence Archive.

Mass shootings have been rising in recent years, as have other kinds of gun violence, making firearms a major public health issue. This year alone, more than 21,000 people have died due to gun violence. Of those deaths, 12,210 were suicides.

But the public health impact of gun violence extends far beyond those who are killed or injured. A far larger number of people are left grieving, traumatized, and at a risk of long-term struggles with a range of mental health issues.

"Any time a community is impacted by large-scale mass violence, the community is changed forever," says psychologist Robin Gurwitch at Duke University. "The names of those communities are now linked to mass violence, whether it is Sandy Hook, or whether it is Oklahoma City, Columbine. There are so many."

Studies show that people closest to gun violence, who witness it, or are injured, or who lose a loved one or an acquaintance, or even who have a loved one who was present at an incident, are at highest risk of mental health impacts, she adds.

A recent poll by KFF (formerly the Kaiser Family Foundation) found that a significant number of Americans have had a direct experience of gun violence. Nearly 1 in 5 adult respondents to the poll said they've lost a family member to gun violence, and a similar number said they have witnessed someone being shot. Those numbers are even higher in communities of color.

But recent research also shows that "members of the community are also impacted even if they didn't know someone," Gurwitch says.

A recent study by the Children's Hospital of Philadelphia found that children within a five-block-radius of a shooting were more likely to end of up in a hospital emergency room in the weeks after the shooting, with symptoms of mental health problems like anxiety and suicidal thoughts.

In the immediate aftermath of gun violence, people in affected communities often experience symptoms of "acute stress," says psychologist Julie Kaplow, executive vice president of trauma and grief programs and policy at the Meadows Mental Health Policy Institute in Texas.

"People are hyper vigilant, are on edge, may have trouble sleeping or eating, may be extremely nervous to leave loved ones," says Kaplow, who has assisted communities affected by both the Santa Fe high school shooting in 2018, as well as the mass shooting last year at an elementary school in Uvalde, Texas.

That sense of hyper vigilance due to gun violence is something that has spread across the country, according to Don Rodricks, a columnist at the Baltimore Sun. He remembers catching himself looking for the exits at a concert he attended with his family in recent years, "in case something were to happen," he told NPR's Steve Inskeep following the shooting in Baltimore on Sunday.

"It does affect how you think when you go out into the world," he added. "Young parents worried about their kids in school, whether there's going to be a mass shooting [at] a prayer service. I mean, 10-20 years ago, you wouldn't have thought about the danger in doing that."

The good news here, says Kaplow, is most people recover from these symptoms over time. But a significant minority, "typically 25% of individuals," she says, continue to experience symptoms long term.

"Some of those include re-experiencing — feeling like the event is happening all over again, avoidance, not wanting to talk about or think about what happened. Numbing, where they may literally feel like they don't have any feelings," Kaplow says.

Adults can also develop some behavioral health issues like substance abuse, social withdrawal and even suicidal thoughts.

And children who have experienced gun violence are also at a risk of long-term mental health issues, especially those with certain preexisting risk factors.

"For example, we know that kids who have experienced prior traumas or losses are at a higher risk for developing longer-term PTSD," Kaplow says. And these kids are more likely to be from communities of color, which are at a higher risk of experiencing chronic violence and also deaths from other causes.

"We also know that those that have very little social support or those who have already had significant mental health issues prior to the event like anxiety or depression."

Kids are also at a higher risk of long-term mental health problems when their parents and/or caregivers don't get the support they need, Kaplow explains.

"Children are sponges and they absorb everything they're seeing and hearing in their environment," she says. "And if that includes a caregiver who is very panicked or very anxious about what's going on, that can greatly impact how the child feels."

And so, providing social and mental health support to the adults in children's lives is key to helping communities recover from the trauma of gun violence, she says.

Long-term bereavement support is also key, Kaplow adds.

"We know that for these communities, while the trauma may recede over time, and it usually does, the grief remains. And that is an area that receives very little attention."

This is where community-based and faith-based organizations can play a big role in healing communities from the potential long-term effects of gun violence, she says.