(CNN)One month ago, our concept of horrific mass shootings reached a new extreme.
Ten minutes of gunfire ended the lives of 58 country music fans on the Las Vegas Strip. It was the deadliest mass shooting in modern US history.
But unlike mass shootings of the past, we still know very little about why it happened. Here's what we're learning, and what's still unknown:
What was the gunman's motive?
The answer remains elusive, and may never surface.
"Usually within 24, 48 hours after an incident like this, we generally know what the motive is," said CNN law enforcement analyst Art Roderick, a retired assistant director of the US Marshals Service.
But gunman Stephen Paddock, 64, was an unusual mass killer. He was a wealthy retiree. He didn't have any known ties to radical political or extremist groups. He left no writings or other clues about what prompted him to inflict widespread carnage.
"In my opinion, I think he doesn't want us to know. He wants us to continue to ask these questions," Roderick said. "This is a unique case. This individual is almost in a category by himself."
On Tuesday, the FBI declined to give updates on the case, saying the investigation is ongoing.
What's the latest on the timeline?
Police have made multiple changes to their timeline of events on October 1, the night Paddock shot a Mandalay Bay security guard and fired into a crowd of 20,000 festivalgoers across the street.
Las Vegas police say the most recent timeline shows Paddock shot Mandalay Bay security guard Jesus Campos at or around 10:05 p.m., about the same time Paddock started firing into the crowd.
That timeline now closely aligns with the account given by Mandalay Bay owner MGM, which disputed a previous police timeline saying Campos was shot and wounded six minutes before the massacre started.
Clark County Sheriff Joe Lombardo said changes to initial reports can happen during complex investigations.
"Nobody is attempting to hide anything (in) reference to this investigation," he said.
"The dynamics and the size of this investigation requires us to go through voluminous amounts of information in order to draw an accurate picture. My attempt, like I stated earlier, is to give you information as I know it, unverified, to calm the public -- not to establish a legal case."
What happened to the killer's girlfriend?
Paddock's girlfriend, Marilou Danley, was in the Philippines at the time of the attack. She voluntarily flew back to the United States after the massacre, Danley said in a statement released by her attorney.
Danley said Paddock had bought her a ticket to see her family in the Philippines and later wired her money to buy a house. At first, Danley said, she was worried Paddock was trying to break up with her.
"It never occurred to me in any way whatsoever that he was planning violence against anyone," her statement said.
Since her return to the United States, Danley has spoken to investigators multiple times, Lombardo said.
But it's unclear what details she has given authorities. Las Vegas police did not respond to requests for comment on Tuesday, and the FBI declined to give updates on the case, saying the investigation is ongoing.
What changes have been made since the shooting?
Not many. Shortly after the shooting, lawmakers from both parties said it was time to re-evaluate bump stocks, legal devices that can make semi-automatic weapons unleash bullets with about the same speed as fully automatic weapons.
Even the National Rifle Association said bump stocks "should be subject to additional regulations."
But so far, bills that would ban bump stocks have stalled.
Nine Republican senators sent a letter to the Bureau of Alcohol, Tobacco, Firearms and Explosives asking the agency to review its policy on bump fire stocks.
A spokeswoman for the ATF told CNN on Tuesday that Senate judiciary committee staffers were briefed by the ATF regarding bump stock related matters, but had nothing further to add.
When asked about the status of bump stock regulation on Tuesday, GOP Sen. John Thune's office referred to the letter, which he was involved in. But there appeared to be no new developments.
How many victims are still hospitalized?
About 500 people suffered injuries in the attack, ranging from gunshot wounds to stampede injuries.
As of Tuesday, at least three victims remained hospitalized. Two were in the intensive care unit at Sunrise Hospital, and one victim was at St. Rose Dominican Hospital.
Has anyone sued?
The father of Andrea Castilla, a 28-year-old California woman killed in the attack, has filed a lawsuit against MGM, Mandalay Corp., Live Nation Entertainment, and the estate of Stephen Paddock, among others.
"As to the hotel defendant, it's inconceivable to us that someone was capable of transporting what amounts to an armory of weapons into the hotel," attorney Richard Bridgford said.
"As to the security -- provided at the concert and the Live Nation defendants -- the witnesses with whom we've spoken claim that after the shooting began -- the exits were insufficient and poorly marked."
Bridgford said he believes the mass shooting was "entirely avoidable."
What will happen to the gunman's hotel room?
No one else will stay there for the foreseeable future.
"This was a terrible tragedy perpetrated by an evil man," the company said. "We have no intention of renting that room."