US Senator Edward Markey delivered a blistering call Friday for lawmakers to pass stricter gun control measures, saying the worst mass shooting in modern US history should compel them to act boldly.

On the heels of his participation in Senate Democrats’ 15-hour filibuster that ended early Thursday, Markey said at a news conference attended by gun control activists that the impending votes on gun control measures will hold other senators accountable.

On Monday, just over a week after the Orlando massacre, the US Senate is expected to vote on a bill to prohibit people who are on a federal “no-fly’’ list from buying guns, and on an amendment to require broader use of background checks in gun sales.

“It’s time for us to have a showdown on the floor of the United States Senate,’’ Markey said at the news conference, at Fenway Health.

However, he also said he has yet to see signs of compromise from the Republicans. Later, Markey said that whether or not these amendments pass, they will serve as a litmus test for voters come election season.

John Rosenthal, head of the Newton-Based group Handgun Violence, joined Markey. He pulled no punches.

“The gun industry is getting away with murder because Congress allows it,’’ Rosenthal said. “Congress has blood on their hands.’’

Markey and other members of the Massachusetts congressional delegation have ratcheted up pressure on other lawmakers for tougher gun control measures in the days following the Orlando killings.

And this time, he said, will be different. Markey predicted that the Orlando slayings — unlike mass shootings in Newtown, Aurora, San Bernardino, and other places — will reverberate through the halls of the Capitol.

“I think everything changed in Orlando,’’ he said.

Monalisa Smith, who lost her nephew to gun violence, said the shooting epidemic isn’t confined to terrorist acts.

“What happened in Orlando was horrible,’’ said Smith, head of Massachusetts-based Mothers for Justice and Equality. “But what happens on the streets of our urban centers is just as bad.’’

Bostonians don’t have far to look for evidence of this, she said, noting last week’s killing of 17-year-old Raekwon Brown outside Jeremiah E. Burke High School.

Dr. William Begg, an emergency room physician from Newtown, Conn., also invoked the victims of gun violence in his remarks at the news conference. Begg was working in the ER after the mass shooting at Sandy Hook Elementary School.

“I witnessed the unspeakable,’’ he said at the news conference. “Children of my friends and my neighbors were shot multiple times in their classroom with an assault weapon.’’

Begg said that, in the past, Congress has taken a reactive, not a proactive, approach to gun violence. Like Markey, Smith is hopeful that Orlando will mark a turning point.

And if it doesn’t?

Well, Smith said, she’ll keep on fighting.

“It’s the filibuster we’re on for a lifetime.’’

Reis Thebault can be reached at reis.thebault@globe.com. Follow him on Twitter at @reisthebault.