The father of a student killed in the Columbine High School massacre 13 years ago spoke out Friday on the latest gun carnage, this time at a movie theater in another Denver suburb, and asked, "How many more of these do we have to endure before we say this is enough?"

Tom Mauser's 16-year-old son Daniel was among 13 people slaughtered in the school in a hail of gunfire that shocked the nation in 1999. In a phone interview with The Huffington Post, the Littleton, Colo. father said he didn't think he knew anyone who was killed or injured 17 miles away in Aurora but he does have a sense of what the families touched by the tragedy must be going through.

"It's shocking. It's awful that we have this kind of massacre happening in Colorado again," he said. "When it’s a large number like this and the same thing .... it brings it home in a big way. It’s a real kick to the groin."

"I'm hoping that we get more out of our leaders than simply words of sympathy. We’ve had enough of this kind of thing and we’re looking for something more than just words and sympathy."

After his son died, Mauser got involved in pushing for stricter gun laws. He worked to close the gun show loophole that allowed the Columbine killers to buy their guns without going through a background check. After the Colorado legislature failed in 2000 to pass the needed legislation, Mauser became a spokesman and lobbyist for a group leading the effort to put Amendment 22 on the ballot. The measure to require background checks at gun shows passed overwhelmingly, with 70 percent of voters approving.

"That clearly showed that people will support reasonable gun laws," he said. "The problem is legislators won't do that. They are so afraid of the gun lobby."

Mauser, who works for the Colorado Department of Transportation, has remained active on the gun issue. He is on the board of Colorado Ceasefire, a gun control advocacy group in Denver.

In 2006, he campaigned to elect Aurora's current congressman, Ed Perlmutter, who supports stricter gun laws. Perlmutter's Republican challenger this November, beer magnate Joe Coors, has been endorsed by the National Rifle Association.

Mauser took note that the alleged Aurora shooter had an assault rifle with a magazine holding multiple rounds. Congress "shamefully allowed the assault-weapons ban to expire" in 2004. "There is no reason to have these military weapons in the hands of civilians," he said. "It's crazy."

The movie theater massacre, the deadliest since 32 people died in a mass shooting at Virginia Tech, is just the latest gun violence to cause Mauser to reflect on his own loss.

"We’ve seen mass shootings in just about any place you can imagine: movie theaters, bars, nursing homes, schools," he said, noting more people die in gun violence every day that the death toll so far in Aurora. "People see cases like this and say 'it's really terrible but let's not change our gun laws.' "

"I think Americans have simply come to learn to accept this level of violence and many don’t realize that most other developed nations don’t have this kind of problem. It's easy to say this is the price you pay for our freedoms when it's not your child or your neighbor or your friend."

Mauser recently self-published a book, "Walking in Daniel's Shoes." It's about his journey as an advocate who literally wears the shoes his son had on when he died as he goes out to speak about the need to fight back against the gun lobby and its interests.

Mauser, who has a daughter born two years after Daniel, offered some advice to to the families of those killed in the "Batman" premiere.

"The primary thing I would say is do something to honor your loved one. That’s what I did. I didn’t want my son to be forgotten."

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  • 1981: The Attempted Assassination Of President Ronald Reagan

    on March 30, 1981, President Reagan and three others were shot and wounded in an assassination attempt by John Hinckley, Jr. outside the Washington Hilton Hotel in Washington, D.C. Reagan's press secretary, Jim Brady, was shot in the head.

  • 1993: The Brady Handgun Violence Act

    The Brady Handgun Violence Act of 1993, signed into law by President Bill Clinton, mandated that federally licensed dealers complete comprehensive background checks on individuals before selling them a gun. The legislation was named for James Brady, who was shot during an attempted assassination of President Ronald Reagan in 1981.

  • 1994: The Violent Crime Control and Law Enforcement Act

    The Violent Crime Control and Law Enforcement Act, signed into law by President Bill Clinton in 1994, instituted a ban on 19 kinds of assault weapons, including Uzis and AK-47s. The crime bill also banned the possession of magazines holding more than ten rounds of ammunition. (An exemption was made for weapons and magazines manufactured prior to the ban.)

  • 2004: Law Banning Magazines Holding More Than Ten Rounds Of Ammunition Expires

    In 2004, ten years after it first became law, Congress allowed a provision banning possession of magazines holding more than ten rounds of ammunition to expire through a sunset provision. Brady Campaign President Paul Helmke told HuffPost that the expiration of this provision meant that Rep. Gabby Giffords's alleged shooter was able to fire off 20-plus shots without reloading (under the former law he would have had only ten).

  • 2007: The U.S. Court of Appeals For The District Of Columbia Rules In Favor Of Dick Heller

    In 2007 The U.S. Court of Appeals for the District of Columbia ruled to allow Dick Heller, a licensed District police officer, to keep a handgun in his home in Washington, D.C. Following that ruling, the defendants petitioned the U.S. Supreme Court to hear the case.

  • 2008: The NICS Improvement Amendments Act

    Following the deadly shooting at Virginia Tech University, Congress passed legislation to require states provide data on mentally unsound individuals to the National Instant Criminal Background Check System, with the aim of halting gun purchases by the mentally ill, and others prohibited from possessing firearms. The bill was signed into law by President George W. Bush in January of 2008.

  • 2008: Supreme Court Strikes Down D.C. Handgun Ban As Unconstitutional

    In June of 2008, the United States Supreme Court upheld the verdict of a lower court ruling the D.C. handgun ban unconstitutional in the landmark case <em>District of Columbia v. Heller</em>.

  • Gabrielle Giffords And Trayvon Martin Shootings

    Gun control advocates had high hopes that reform efforts would have increased momentum in the wake of two tragic events that rocked the nation. In January of 2011, Jared Loughner opened fire at an event held by Rep. Gabrielle Giffords (D-Ariz.), killing six and injuring 13, including the congresswoman. Resulting attempts to push gun control legislation <a href="" target="_hplink">proved fruitless</a>, with neither proposal even succeeding in gaining a single GOP co-sponsor. More than a year after that shooting, Florida teenager Trayvon Martin was <a href="" target="_hplink">gunned down</a> by George Zimmerman in an event that some believed would bring increased scrutiny on the nation's Stand Your Ground laws. While there has been increasing discussion over the nature of those statutes, lawmakers were <a href="" target="_hplink">quick to concede</a> that they had little faith the event would effectively spur gun control legislation, thanks largely to the National Rifle Association's vast lobbying power. Read more <a href="" target="_hplink">here</a>:

  • Colorado Movie Theater Shooting

    In July of 2012, a heavily armed gunman <a href="" target="_hplink">opened fire on theatergoers</a> attending a midnight premiere of the final film of the latest Batman trilogy, killing 12 and wounding scores more. The suspect, James Eagan Holmes, allegedly carried out the act with a number of handguns, as well as an AR-15 assault rifle with a 100-round drum magazine. Some lawmakers used the incident, which took place in a state with some of the laxest gun control laws, to bring forth legislation designed to place increased regulations on access to such weapons, but many observers, citing previous experience, were <a href="" target="_hplink">hesitant to say</a> that they would be able to overcome the power of the National Rifle Association and Washington gun lobby.

  • Sikh Temple Shooting

    On August 5, 2012, white supremacist Wade Michael Page opened fire on a Sikhs gathered at a temple in Oak Creek, Wis., killing six and wounding four more before turning the gun on himself.