They had more in common than unleashing carnage _ nearly every gunman in this monthlong series of mass killings was legally entitled to fire his weapons.
So what does that say about the state of gun control laws in this country? One thing appears certain: the regulations aren't getting stricter. Many recent efforts to change weapons laws have been about easing them.
Despite eight rampages that have claimed 57 lives since March 10, "it hasn't sparked any national goal to deal with this epidemic. In fact, it's going the other way," said Scott Vogel of the Freedom States Alliance, a gun control activist group.
Even President Barack Obama has felt that sway. Last month, 65 House Democrats said they would block any attempt to resurrect an expired federal ban against assault weapons.
The pro-gun Democrats, led by Rep. Mike Ross of Arkansas, wrote Attorney General Eric Holder saying they opposed not only a ban on military-style guns, but also efforts "to pass any similar law."
Gun control issues would only produce "a long and divisive fight," they said, at a time when Congress should be focused on the roiling economy.
A few states are trying to loosen gun restrictions. In the Texas Capitol _ where legislators can carry guns _ bills easily passed the Senate in recent weeks that would allow employees to bring weapons to work as long as they leave them locked in their cars, and let those packing heat off the legal hook if they walked into a bar that didn't have signs saying guns weren't allowed inside.
The state also is considering allowing students licensed to carry a concealed weapon _ there are about 300,000 such adults in Texas _ to bring guns on campus.
Kansas plans to put a measure on its 2010 ballot that would rewrite the state constitution to make gun ownership a personal, rather than collective, right. In Tennessee, lawmakers made progress this month toward allowing guns to be carried in state and local parks.
"I think you're seeing a continuing change of culture," Vogel said. "I think the gun lobby wants to take away any stigma to gun ownership. I think they feel emboldened, like who's going to stop them?"
The National Rifle Association, the country's most powerful gun lobbying group, declined to comment this week on gun control laws. "Now is not the time to debate politics or discuss policy. It is time for families and communities to grieve and to heal," it said in a prepared statement.
Groups such as Vogel's, and the Brady Campaign to Prevent Gun Violence, say existing laws are already too weak _ just look at the men who received gun permits, legally bought high-powered weapons, and then mowed down family, friends and total strangers in these past few weeks, they say.
Joining their outrage was the U.S. Conference of Mayors. "How many more gun-related acts of violence must we experience before the nation's leaders will decide that it is time to act?" asked president Manuel Diaz, mayor of Miami.
Gun enthusiasts say there is no way to prevent human beings from committing insane acts _ whether they have a gun permit or not. And studies conflict on whether stricter gun laws lessen gun violence.
On Friday, a depressed and angry Jiverly Wong used a 9 mm and .45-caliber handgun to kill 13 immigrants and service center employees in Binghamton, N.Y., police said. Earlier that day, the ethnic Chinese immigrant from Vietnam mailed an envelope to a Syracuse television station. In it were his gun permit, photos of him smiling while hoisting shiny, big handguns, and his driver's license.
Questions have been raised over the upstate New York gun permit issued to Wong in 1997. Two years later, he was reported to state police by an informer who claimed Wong was planning a bank heist to feed a crack-cocaine habit. Unlike other areas of the state, including New York City, Wong's Broome County permit did not have to be renewed.
Local authorities, however, have broad discretion in reviewing and revoking such permits, according to legal experts. Especially when it comes to drug use, criminal behavior and violence.
"In retrospect, this is probably not a guy who should have had a gun," said attorney Jeffrey Chamberlain, a former Rochester prosecutor and chief counsel to the New York State Police. "No one likes to see things fall through the cracks and it looks like this guy fell through the cracks."
Binghamton police chief Joseph Zikuski said Tuesday that no robbery occurred and there was no merit to review Wong's gun permit.
In New York City, gun permits are reissued every three years.
Yet, regulations differ only slightly between states, Chamberlain said. "They're fairly typical _ don't be a felon, don't be a drunk, don't beat your kids or your wife. Don't be so mentally unbalanced that you need be in an institution."
To Chamberlain, the answer to gun violence lies not in stricter regulations, but in answering the question, "Why are we so tolerant of having guns in this country? The answer to that is historical. We've had guns for a very long time.
"I can't think of any sweeping law change that would address that."
To Vogel, the answer to why atrocities happen in places such as Binghamton, and before that Washington state and Santa Clara, Calif., lies in sheer numbers.
The number 280 million, to be precise, the estimated total of every gun in this country.
"When you have that many guns, those guns are going to be used in horrific ways," Vogel said. "There's just too many. Inevitably, somehow, some way, those weapons are going to be used in an egregious way."