Since 2009, at least 177 of America’s schools experienced a shooting. These tragedies are as diverse as our nation, but the depth of trauma is hard to convey. There is no standard definition for what qualifies as a school shooting in the US. Nor is there a universally accepted database. So CNN built our own. We examined 10 years of shootings on K-12 campuses and found two sobering truths: School shootings are increasing, and no type of community is spared.

10 years of school shootings Killed Killed Injured Injured 2009 5 killed 14 injured William Penn High School (New Castle, DE) Dunbar Vocational Career Academy (Chicago, IL) Cahokia High School (Cahokia, IL) Zebulon Middle School (Zebulon, NC) Central High School (Detroit, MI) Westover High School (Fayetteville, NC) Chimborazo Elementary School (Richmond, VA) Leestown Middle School (Lexington, KY) Aplington-Parkersburg High School (Parkersburg, IA) Mattituck High School (Mattituck, NY) Wilson High School (Long Beach, CA) Brockton High School (Brockton, MA) Booker T. Washington High School (Shreveport, LA) 2010 4 killed 7 injured Livingston High School (Livingston, AL) Discovery Middle School (Madison, AL) Inskip Elementary School (Knoxville, TN) Deer Creek Middle School (Littleton, CO) Birney Elementary School (Tacoma, WA) South Gate High School (South Gate, CA) Alisal High School (Salinas, CA) Kelly Elementary School (Carlsbad, CA) 2011 3 killed 18 injured Millard South High School (Omaha, NE) Gardena High School (Gardena, CA) Louisiana Schnell Elementary School (Placerville, CA) Martinsville West Middle School (Martinsville, IN) Worthing High School (Houston, TX) Sheeler Charter High School (Apopka, FL) Ross Elementary School (Houston, TX) Highlands Intermediate School (Pearl City, HI) Horizon Elementary School (Everett, WA) Chandler Park Academy (Harper Woods, MI) Cape Fear High School (Fayetteville, NC) Harwell Middle School (Edinburg, TX) 2012 31 killed 8 injured North Forest High School (Houston, TX) Armin Jahr Elementary (Bremerton, WA) Chardon High School (Chardon, OH) Episcopal School of Jacksonville (Jacksonville, FL) Mary Scroggs Elementary School (Chapel Hill, NC) Perry Hall High School (Baltimore, MD) Sandy Hook Elementary (Newtown, CT) 2013 6 killed 11 injured Taft High School (Taft, CA) Price Middle School (Atlanta, GA) Hillside Elementary School (San Leandro, CA) Redland Middle School (Homestead, FL) Alexander W. Dreyfoos School of the Arts (West Palm Beach, FL) North Panola High (Sardis, MS) Agape Christian Academy (Pine Hills, FL) Sparks Middle School (Sparks, NV) Stephenson High School (Stone Mountain, GA) West Orange High School (Winter Garden, FL) Arapahoe High School (Centennial, CO) Edison High School (Fresno, CA) 2014 12 killed 16 injured Liberty Technology Magnet High School (Jackson, TN) Berrendo Middle School (Roswell, NM) Valley Charter High School (Philadelphia, PA) North High School (Des Moines, IA) Salisbury High School (Salisbury, NC) Raytown Success Academy (Raytown, MO) Madison Parish High School (Tallulah, LA) East English Village Preparatory Academy (Detroit, MI) St. Mary Catholic School (Griffith, IN) Paul Robeson High School (Chicago, IL) Horizon Elementary School (Everett, WA) Clarke Street Elementary School (Milwaukee, WI) Reynolds High School (Troutdale, OR) Kelly High School (Benton, MO) Stellar Leadership Academy (Miami, FL) Fern Creek High School (Louisville, KY) Albemarle High School (Albermarle, NC) Langston Hughes High School (Fairburn, GA) Marysville-Pilchuck High School (Marysville, WA) Miami Carol City High School (Miami Gardens, FL) 2015 3 killed 22 injured Kinston High School (Kinston, NC) Wisconsin Lutheran High School (Milwaukee, WI) Williamson High School (Mobile, AL) Vanguard High School (Ocala, FL) Norris Middle School (Omaha, NE) Frederick High School (Frederick, MD) Tenaya Middle School (Merced, CA) Judson High School (Converse, TX) Duval County school bus (Jacksonville, FL) Elolf Elementary School (Converse, TX) W.S. Hornsby K-8 School (Augusta, GA) Dulaney High School (Lutherville Timonium, MD) Northside High School (Lafayette, LA) Central Elementary School (Statesville, NC) Harrisburg High School (Harrisburg, SD) Excel Southwest High School (Chicago, IL) Sulphur Rock STEM Magnet elementary school (Sulphur Rock, AR) 2016 5 killed 46 injured Harmony Grove High School (Camden, AR) Lawrence Central High School (Indianapolis, IN) Whites Creek High School (Whites Creek, TN) Muskegon Heights High School (Muskegon (Muskegon Heights), MI) Independence High School (Glendale, AZ) Faribault Middle School (Faribault, MN) Madison Jr/Sr High School (Middletown, OH) Huffman High School (Birmingham, AL) East High School (Pueblo, CO) High Point High School (Beltsville, MD) Southside High School (Greenville, SC) Augusta High School (Augusta, KS) Thompson K-8 International Academy (Southfield, MI) Technical High School (Saint Cloud, MN) Woodrow Wilson Junior High School (Hanford, CA) Sandusky High School (Sandusky, OH) Chaffey High School (Ontario, CA) Ava High School (Ava, MO) Wedgewood Middle School (Columbus, OH) McLain High School (Tulsa, OK) Alpine High School (Alpine, TX) Kearns High School (Salt Lake City (Kearns), UT) Smalls Athletic Field (York, PA) T.A. Wilson Academy (Jackson, MI) Elder High School (Cincinnati, OH) Townville Elementary (Townville, SC) Vigor High School (Prichard, AL) Linden-McKinley STEM Academy (Columbus, OH) Benjamin E. Mays High School (Atlanta, GA) June Jordan School for Equity (San Francisco, CA) Mott Hall Charter School (Bronx, NY) Union Middle School (Sandy, UT) Houston Can Academy (Houston, TX) Savannah High School (Savannah, GA) Bayless High School (Saint Louis, MO) 2017 8 killed 32 injured West Liberty-Salem High School (West Liberty, OH) Mark Twain Elementary School (Detroit, MI) Scullen Middle School (Naperville, IL) South Aiken High School (Aiken, SC) Palmer Pillans Middle School (Mobile, AL) Lee High School (Montgomery, AL) King City High School (King City, CA) Linton Middle School (Pittsburgh (Penn Hills), PA) North Park Elementary School (San Bernardino, CA) Booker T. Washington High School (Tulsa, OK) Moss Bluff Elementary (Lake Charles (Moss Bluff), LA) McLain High School (Tulsa, OK) Warren Elementary School (Chicago, IL) JFK Stadium (Springfield, MO) North Little Rock High School (North Little Rock, AR) Freeman High School (Rockford, WA) Mattoon High School (Mattoon, IL) Callaway High School (Jackson, MS) Southern Middle School (Lexington, KY) Rocky Mount High School (Rocky Mount, NC) Pattengill Academy (Lansing, MI) Banneker High School (Atlanta, GA) Rancho Tehama Elementary School (Corning, CA) Aztec High School (Aztec, NM) Champaign Central High School (Champaign, IL) Roosevelt Elementary (Hanford, CA) Beecher High School (Mount Morris, MI) 2018 37 killed 68 injured Italy High School (Italy, TX) Marshall County High School (Benton, KY) Lincoln High School (Philadelphia, PA) Sal Castro Middle School (Los Angeles, CA) Oxon Hill High School (Oxon Hill, MD) Pearl-Cohn Entertainment Magnet High School (Nashville, TN) Marjory Stoneman Douglas High School (Parkland, FL) Huffman High School (Birmingham, AL) Great Mills High School (Great Mills, MD) Gloversville Middle School (Gloversville, NY) Raytown South Middle School (Raytown, MO) Forest High School (Ocala, FL) Highland High School (Palmdale, CA) Mount Zion High School (Jonesboro, GA) Santa Fe High School (Santa Fe, TX) Noblesville West Middle School (Noblesville, IN) Skyline High School (Dallas, TX) Edgewood High School (Edgewood, MD) Lakeside Middle School (Millville, NJ) Antioch High School (Antioch, TN) Palm Beach Central High School (Wellington, FL) Raines High School (Jacksonville, FL) Canyon Springs High School (Las Vegas, NV) Hebron High School (Carrollton, TX) Denali Elementary School (Anchorage, AK) Varina High School (Henrico, VA) Butler High School (Matthews, NC) Simonsdale Elementary School (Portsmouth, VA) Cawood Elementary School (Cawood, KY)

Over the past decade, there were at least 180 shootings at K-12 schools across the US. They happened in big cities and in small towns, at homecoming games and during art classes, as students are leaving campus in the afternoon and during late-night arguments in school parking lots. And they are happening more often. CNN analyzed locations, time of day, type of school and student demographics to better understand how this trauma grips the country. While school shootings disproportionately affect urban schools and people of color, mass shootings are more likely to occur at white, suburban schools. Given what has happened so far this year, the frequency shows no sign of relenting.

School shootings are increasing Elementary , middle and high schools

With little federal data on school shootings, it’s hard to pinpoint what’s behind the recent increase. But law enforcement experts believe one reason could be diminished coping skills, which can prompt people to lash out in violent ways. “Today we have kids who are so isolated inside -- playing video games and glued to their (tablets) and everything else -- that they don’t learn those problem-solving skills,” says Mike Clumpner, a sworn police officer who specializes in active shooter training. “We continually see poor coping skills and poor conflict resolution skills,” agrees former FBI agent Chris Cole, director of threat intervention services at the University of Wisconsin. “And as more of them (shootings) occur, it becomes sort of acceptable as ‘that’s a way I can settle my grievances.’” Regardless of what’s behind this violence, it touches every aspect of school life.

More school shootings happen on Fridays and during the afternoon Victims 1 5 20

Early morning Mon Tue Wed Thu Fri Sat/Sun Midnight 8:00 a.m. 10:00 a.m. 12:00 p.m. 2:00 p.m. 4:00 p.m. 6:00 p.m. Daytime Mon Tue Wed Thu Fri Sat/Sun Midnight 8:00 a.m. 10:00 a.m. 12:00 p.m. 2:00 p.m. 4:00 p.m. 6:00 p.m. Late afternoon and evening Mon Tue Wed Thu Fri Sat/Sun Midnight 8:00 a.m. 10:00 a.m. 12:00 p.m. 2:00 p.m. 4:00 p.m. 6:00 p.m.

From school drop-off on Monday morning to a Saturday night basketball game, shootings can happen any time. But more often, they happen on Fridays. Experts suggest this could be due to tensions that build up over the course of a school week. “If something has transpired to bring you to the breaking point of committing some type of homicidal action … you may not have had any type of decompression time during the school week,” says Clumpner. “And so that’s kind of five days stacked on top of each other.” These shootings have tragic effects that ripple beyond the victims and their families. Nearly 200,000 students attended schools where one of these shootings occurred.

Race plays a factor in when school shootings are likely to occur Student body is mostly white Killed Injured KilledInjured Student body is mostly black

At predominately black schools, students are more likely to experience a shooting after 4 p.m., typically during an after-school event. And while black students make up about 15% of the more than 50 million students in the US, they account for about a third of the students who experienced a school shooting since 2009. Meanwhile, shootings at predominately white schools often happen in the morning, as classes begin, or around dismissal time. And those shootings tend to claim more victims.

Shootings at mostly white schools have more casualties Victims 1 3 5

Majority white Majority black Majority hispanic

CNN’s review found that shootings at predominately white schools have an average of three casualties. That's twice the average of the number of shooting victims at predominantly black and Hispanic schools. Mostly white schools also have more mass shootings, like the ones at Marjory Stoneman Douglas High School and Sandy Hook Elementary, typically carried out by young white males while school is in session.

The average shooting has 2 victims 171 Shootings with three victims or fewer. 9 Shootings with four or more victims.

Experts say that while mass shootings are a concern, it's the day-to-day violence that impacts our schools more. “Those mass shootings, the headline-grabbing ones, are really, really a small fraction of them," says Cole. "It’s more of the everyday violence, that unfortunately I think we’ve become a bit immune to, that produce the large numbers.” And this violence reaches across America, touching every kind of community.

Across America, schools saw 356 shooting victims Victims 1 5 20

Suburban Shootings at suburban schools tend to have more casualties. Rural Shootings in rural areas tend to happen at white-majority schools. Urban School shootings disproportionally impact cities.

From the countryside to big cities, 114 people were killed and 242 were injured in shootings at K-12 schools from 2009 through 2018. To prevent school shootings, experts agree we need comprehensive and reliable data. Without that research, we’re going blind into a “deadly future,” cautions Mark Rosenberg, who worked at the Centers for Disease Control and Prevention for 20 years and led its gun violence research. “You need those interventions that reduce gun violence and save lives, but that also protect the rights of law-abiding gun owners,” says Rosenberg. “But we don’t know what works … and we’re not looking. That’s the disgrace.” Editor's Note: CNN spent more than a year analyzing the rising toll of America’s school shootings. CNN will update its database throughout the school year, with 2019 numbers to come.