Two days before Thanksgiving 1994, my only brother, FBI Special Agent Mike Miller, was working at the Metropolitan Washington Police headquarters with two FBI agents and a highly decorated police sergeant. They were in a room whose door was marked "Cold Case Homicides."

That morning, a man under investigation for a triple homicide walked into police headquarters in search of the office of the chief of homicide. Hopped up on drugs and anxiety, he saw the word "Homicide" on the door of  the room where Mike was working. He opened the door, pulled out the MAC-10 semi-automatic assault pistol he had concealed under his jacket, and opened fire.

Mike was the first to die, with a shot to the head. The others were shot and killed in a barrage from the gun's 30-bullet ammunition magazine.  Soon afterward, the shooter finished off the carnage by committing suicide.

One man intent on mayhem had sufficient firepower to overwhelm a room full of trained and armed law officers.

How could such a horrific thing happen? Because our country, alone among all developed countries, allows civilians to acquire semi-automatic assault guns.

Why? Because cowardly politicians worry more about losing favor with the gun lobby and its patrons and funders in the gun industry than about the lives lost to these powerful and dangerous weapons.

One of these kowtowing politicians is Pennsylvania's own U.S. Sen. Pat Toomey, who has declined to support, much less cosponsor, U.S. Senate Bill 2095, a new federal assault weapons ban. Toomey has made much hay of his 2013 sponsorship of a bill to expand some background checks, which almost all of his Republican colleagues opposed. However, that bill included a dangerous giveaway to the gun industry, and Toomey refuses to support an assault weapons ban.

To those of Toomey's ilk who tout the gun makers' and sellers' claim that semi-automatic assault guns are "sporting guns," important for hunting and target shooting, I say, in Mike's memory: Hogwash! What sport is there in using a 30- or even 50-bullet magazine to hunt an animal?

And, obviously, this issue is so much larger than hunting for sport. By not supporting the assault weapons ban, Toomey and his colleagues ignore the toll on human life.

Just citing the names of the sites of these terrible assault-weapon massacres brings a chill of despair: Orlando's Pulse Nightclub; a music festival on the Las Vegas Strip; a church in Sutherland Springs, Texas; a high school in Parkland, Fla..

Must we tolerate the death, destruction, grief, and everlasting trauma just so some may have fun with their assault guns, gun makers and sellers can enjoy the fruit of that carnage, and politicians can continue to benefit from the monetary support that comes from the gun industry?

I am glad that so many people, like the students in Parkland, are saying no that question —  and saying it loudly and with determination to bring lifesaving change to this country. They are demanding a new and effective assault weapons ban, a law favored by a strong majority of Americans.

You can say no to Pat Toomey and his colleagues, too, by joining my organization and other gun-control advocates at Demand the Ban in Philadelphia. We have been planning this event for six months — but its timing could not be more appropriate. At Demand the Ban, we will publicly melt down an assault rifle, turning an instrument of death into one of life, a hand-plow garden implement.  Hundreds will march through the streets of Philadelphia en route to a rally at Toomey's office, carrying a Memorial to the Lost as well as T-shirts on frames, each marked with the name, age, and date of death of the innocents massacred in Orlando, Las Vegas, Sutherland Springs, and Parkland. If denied an opportunity to meet with Toomey to seek to persuade him to cosponsor S.B. 2095, many of us will stage a sit-in until we are heard.

I'll be there in Mike's honor.  I hope you'll be there, too.

Bryan Miller is executive director of Heeding God's Call to End Gun Violencebryanheeding@gmail.com You can register for Demand the Ban at demandtheban.org.