Our nation mourns the victims of the horrific tragedy that transpired at the Boston Marathon on Monday. The full force of the FBI, Boston Police, and intelligence agencies are committed to tracking down, and bringing to justice, the perpetrator or perpetrators responsible. This vile act of terrorism also underlines the responsibility we as citizens have to report suspicious activity to law enforcement – our best first defense against terrorists. If you “see something, say something.”

What occurred in Boston is a sad reminder that terrorist threats are a part of all our lives. But they will not damper the American spirit that defines us. Even in the midst of chaos, first responders, volunteers, runners, and spectators rushed to the bomb site to help the injured, putting the lives of their fellow man ahead of their own personal safety. That instinctive call to action to help our fellow citizens is part of what makes this country great, and why no act or acts of terror will ever break us.

This week also marked the sad milestone of a horrible massacre that occurred close to home, in Blacksburg, Virginia. On April 16, 2007, 32 students and teachers were murdered on the campus of Virginia Tech in a senseless act of gun violence.

In the six years since the massacre at Virginia Tech, over 180,000 people have been killed by gun violence, including murders, suicides, and accidental deaths. And last December, our nation was once again reminded of the fragility of human life when 20 young children and 6 adults were murdered in Newtown, Connecticut.

Following the tragedy in Newtown, millions of Americans in communities across the country have joined together to call for improvements in our gun laws.

Over the next few weeks, the Senate will consider legislation to expand background checks to all commercial gun purchases, strengthen gun trafficking laws, and increase funding for school security measures. I am hopeful that the Senate will pass meaningful gun reform legislation and that Republican leadership in the House will allow an up or down vote on the bill.

Expanded checks are the only systematic way to keep guns out of the hands of felons, the severely mentally ill, and other dangerous people. Far from creating new gun laws, mandatory background checks simply allow for the enforcement of laws already on the books. This is a common sense reform that polling shows is supported by 90 percent of the American public, 82 percent of gun owners, and even 74 percent of NRA members.

Now Congress must act. We owe it to the victims at Virginia Tech and everyone whose lives have been touched by the horrors of gun violence to enact sensible gun safety legislation. As we remember the lives lost and forever changed by the massacre six years ago, let us come together as a nation in continued vigilance against gun violence.