A possible militant in Tennessee. A white supremacist in South Carolina. A PhD student dropout sowing terror at a Batman movie in Colorado.
In one day, three alleged or convicted mass killers shared headlines in America, with a common thread running through all their stories - easy access to firearms.
The coincidence has rekindled calls for Congress to finally beef up the nation’s gun laws - something it failed to do after the Newtown, Connecticut elementary school shooting in 2012 that left 20 children dead.
“This is one of the most significant days in American history when it comes to gun violence,” says Dan Gross, president of the Brady Campaign to Prevent Gun Violence.  “The same day a jury handed down its verdict on a man for carrying out mass murder in a Colorado movie theatre, another went on a deadly rampage killing four American Marines,” he said.  “If this doesn’t cause policymakers to stop and think about the impact of gun violence in our country, what will?”
Gross was referring to James Holmes, 27, the one-time post-graduate neuroscience student who killed 12 people and wounded 70 others during a midnight screening of The Dark Knight Rises in Aurora, Colorado in July 2012.
He was convicted on a staggering 165 counts on Thursday, the same day that Kuwaiti-born, American-raised Mohamed Youssuf Abdulazeez, 24, shot and killed four Marines in Chattanooga, Tennessee before dying in a shootout with police.
Gross could also have cited Dylann Roof, 21, charged with the June 17 massacre of nine blacks at the historic Emanuel African Methodist Episcopal Church in Charleston, South Carolina.
Roof, who allegedly hoped the bloodbath would incite a race war, appeared on Thursday in person before a judge who set July 11 next year as the tentative start date for his trial.
Mass killings- defined by the FBI as those with at least four victims - account for only about 1% of all murders in the US, according to an analysis of FBI data by the newspaper USA Today.  But they nevertheless occur about every two weeks. Often they grip Americans’ imagination like few other crimes.
Under the Constitution, every American is entitled “to keep and bear arms” -  a tenet jealously guarded by millions of law-abiding gun owners as a symbol of liberty and a foil against tyrannical government.
The December 2012 tragedy in Newtown -  in which six educators also died  -  spurred President Barack Obama to demand tighter controls on the sale of military-style assault rifles like the one used by 20-year-old shooter Adam Lanza.
But such is the political clout of the National Rifle Association (NRA) and the gun industry on Capitol Hill that legislation to mandate background checks for all gun sales - not just those at federally licensed gun shops - never cleared the Senate.