On Dec. 14, 2012, a gunman went to Sandy Hook Elementary School in Newtown, Connecticut, and killed 20 first-graders and six school employees before taking his own life.

It wasn’t the first time a mass shooting had shocked the nation, but it was the first elementary school targeted. And the young victims, ages 6 and 7 years old, made it especially difficult. President Obama was brought to tears as he spoke of the shooting.

“As a country, we have been through this too many times,” Obama said. “Whether it’s an elementary school in Newtown, or a shopping mall in Oregon, or a temple in Wisconsin, or a movie theater in Aurora, or a street corner in Chicago -- these neighborhoods are our neighborhoods, and these children are our children. And we’re going to have to come together and take meaningful action to prevent more tragedies like this, regardless of the politics.”

The tragedies have continued to mount and are growing in scale. Six of the 10 the deadliest mass shootings in U.S. history have occurred during the past 10 years, including Sandy Hook. The other five shootings are:

In this Oct. 3, 2017, photo, personal belongings and debris litter the Route 91 Harvest festival grounds across the street from the Mandalay Bay resort and casino in Las Vegas. Singer Jason Aldean was performing as the Route 91 Harvest Festival's final headlining act when the gunfire erupted. AP

Oct. 1, 2017: 58 people are killed and more than 850 are wounded when a gunman opens fire on people attending a country music concert in Las Vegas.

June 12, 2016: 49 people were killed and more than 50 wounded in the shooting at Pulse nightclub in Orlando, Florida.

Nov. 5, 2017: 26 people are killed and 20 injured in the shooting at First Baptist Church in Sutherland Springs, Texas.

Aug. 3, 2019: A shooting at a Walmart in El Paso, Texas, claims the lives of 22 people and wounds 24.

Feb. 14, 2018: A school again is the target when 17 people are killed and 17 wounded in a shooting at Marjory Stoneman Douglas High in Parkland, Florida.

Outside the top 10 but still occurring in the past 10 years:

-- July 20, 2012: 12 are killed and 70 wounded in a shooting at a movie theater in Aurora, Colorado

-- Nov. 7, 2018: 13 are shot and killed and 18 wounded at a bar in Thousand Oaks, California

-- May 20, 2019: 12 die and and four are wounded after a gunman opens fire at the municipal center in Virginia Beach, Virginia

-- Oct. 27, 2018: 11 killed and six wounded at the Tree of Life Synagogue in Pittsburgh, Pennsylvania

-- June 17, 2015: Nine shot dead at Emanuel African Methodist Episcopal Church in Charleston, S.C.

-- Aug. 4, 2019: Nine shot dead and 17 wounded at a nightclub in Dayton, Ohio.

The shootings targeted stores, clubs, churches and schools, including when Daniel Parmertor, Russell King Jr. and Demetrius Hewlin were killed in a shooting at Chardon High School on Feb. 27, 2012.

Search for answers

In this Aug. 3, 2019, file photo, an employee crosses into the crime scene following a shooting at a Walmart in El Paso, Texas. AP

After each shooting, the debate over what is causing the violence is renewed. The usual topics emerge --gun control, mental illness and cultural influences.

After the shootings this year in El Paso and Dayton, President Trump blamed the glorification of violence in the United States. He also targeted video games and called for reforms to mental health laws.

Experts tell USA Today that a blanket of assessment of mental illness in connection with mass shootings is incorrect. Kevin Fischer, the executive director of the Michigan chapter of the National Alliance on Mental Illness, told USA Today that studies show there is little correlation.

“Study after study has shown us that is simply not true. It’s actually more often the reverse,” Fischer said. He says people living with mental illness are far more likely to be victims of violence than perpetrators. “Racism, hate, white supremacy are not diagnosable mental illnesses.”

A report from Columbia University Irving Medical Center says only 3 to 5 percent of violent events can be attributed to mental illness.

In regard to video games, the Columbia report says a recent study found “no association between video games and other types of screen time and gun ownership among teens.”

“Among the 5 percent to 10 percent of American teens who report regularly carrying a firearm, there is a much stronger association with substance use, engagement in physical fighting, and exposure to sexual violence than with any poor mental health indicator," said Sonali Rajan, assistant professor of health education at Columbia University Teachers College, according to the Columbia report.

Gun control

Shootings bring renewed calls for increased gun control. After the shooting in Parkland, several students became advocates for stronger gun laws, leading to the formation of the group March for Our Lives. Families affected by the shooting in Newtown formed Sandy Hook Promise, with the goal of preventing further shootings and other violence in schools.

Efforts for increased gun control largely have been ineffective.

This year, Gov. Mike DeWine introduced gun control measures that would eschew universal background checks in favor of voluntary system for private sellers. The plan also refrains from a red flag law – which would allow judges to order the seizure of guns from people deemed a threat to themselves or others – in favor of expanding the state’s existing pink-slip procedure to persons addicted to drugs or alcohol.

DeWine’s bill has received hearings in the Ohio Senate, but its future is unclear.

A grass-roots group called Ohioans for Gun Safety plans to put a universal background check requirement on the ballot in 2021.

Overall, Columbia researchers say gun laws have become more permissive over the past decades. Most states allow the open carry of firearms, although restrictions vary from state to state. In Ohio, people who legally own a firearm can carry openly with or without a concealed handgun license, according to the Ohio Bar Association.

More states also have expanded “Stand your ground” laws, which allow a person to use force without retreating if they feel threatened. “Stand your ground” legislation currently was reintroduced in Ohio. In addition, at least 43 schools in Ohio now allow teachers and staff to carry firearms, according to the Dayton Daily News.

Those arguing for more permissive gun laws say it will reduce the threat of mass shootings, that a “good guy with a gun” could act to stop a shooter. Columbia researchers disagree, saying that states with more permissive gun laws have seen higher rates of mass shootings (defined as four or more people killed by a firearm) than states with more restrictive gun measures.

Access to weapons remains a sticking point, particularly in regard to high-powered semi-automatic rifles such as the AR-15. According to CBS News, there are more than 11 million AR-15s in the country, making it the most popular rife in the nation. CBS reports the AR-15 rarely is used in everyday crime, with handguns the weapon of choice. But a variation of the AR-15 was used in the shootings the Pittsburgh synagogue, Texas church, the Las Vegas concert, Parkland and Newtown.

The federal assault weapons ban expired in 2004. Calls for a renewal of the ban have been ineffective, although several Democratic candidates for president are promising more restrictions on guns. President Trump has said he’s “moving very slowly” in regard to gun legislation, adding he wants "to make sure it’s right.”

‘Thoughts and prayers’

After each shooting, there is an onslaught of “thoughts and prayers” for victims, particularly on social media from politicians. For many, it’s becoming an empty gesture. CNN’s AJ Willingham believes it’s lost its meaning.

“The repetition of ‘thoughts and prayers’ is a product of the repetition of mass shootings,” Willingham says. “And to #ThoughtsAndPrayers critics, the repetition of mass shootings exists because no one is doing much else besides offering thoughts and prayers.”

After the shooting in Dayton this year, Ohio Gov. Mike DeWine attended a vigil for the victims. People in the crowd began shouting “Do something!" as DeWine spoke. Days later, DeWine called for background checks on almost all gun sales in Ohio and for consideration for a “red-flag” law, though his proposal later backed down from these ideas.

The “thoughts and prayers” sentiment still holds meaning to people like conservative commentator Mike Huckabee, who defended the response after the shootings in El Paso and Dayton in a column for Fox News.

“I will continue to pray for the victims and their families and for an end to this mindless violence, and I hope you will, too,” Huckabee says. “In fact, I would posit that the lack of thoughts and prayers is probably the single biggest factor behind these horrors.”