(CNN) Investigators are still trying to pin down Stephen Paddock's motive for opening fire on thousands of country music fans in Las Vegas, killing 58 people and wounding nearly 500 in the worst mass shooting in modern US history.

What they have uncovered -- in his 32nd-floor suite at the Mandalay Bay hotel, his car and his homes -- is a remarkable collection of firearms commensurate with the scale of violence he unleashed before he killed himself as police closed in.

Here's what we know about the weapons cache:

He had 47 guns.

In all, authorities have found 47 guns of varying size and power that belonged to Paddock.

Investigators discovered 23 guns in his hotel room in Las Vegas in the immediate hours after the attack, plus another 24 at his homes in Mesquite and Verdi, Nevada, near Reno.

It's not clear how many guns were rifles or handguns. But at least 12 of those in the hotel room were outfitted with bump stocks , which allowed the semi-automatic weapons to mimic the gunfire of automatic ones, according to Jill Snyder, special agent in charge of the ATF's San Francisco field division.

Such a large collection isn't necessarily unusual, Sam Rabadi, a retired special agent for the Bureau of Alcohol, Tobacco, Firearms and Explosives, told CNN

"There are states in the country where there's a lot of hunting, outdoor activities. There are also areas where you have a higher population of collectors," Rabadi said. "The purchase of that many firearms in and of itself don't necessarily raise red flags for us."

Police also discovered more than 50 pounds of exploding targets and 1,600 rounds of ammunition in Paddock's car in the hotel's parking lot.

He bought most of them recently ...

Paddock was "a man who spent decades acquiring weapons and ammo," Sheriff Joseph Lombardo of the Las Vegas Metropolitan Police Department said during a Wednesday news conference.

Photos: Mass shooting at Las Vegas music festival Debris is scattered on the ground Monday, October 2, at the site of a country music festival held this past weekend in Las Vegas. Dozens of people were killed and hundreds were injured Sunday when a gunman opened fire on the crowd. Police said the gunman fired from the Mandalay Bay hotel, several hundred feet southwest of the concert grounds. It is the deadliest mass shooting in modern US history. Hide Caption 1 of 30 Photos: Mass shooting at Las Vegas music festival Broken windows of the Mandalay Bay are seen early in Las Vegas on Monday. Police said the gunman fired on the crowd from the 32nd floor of the hotel. Hide Caption 2 of 30 Photos: Mass shooting at Las Vegas music festival People cross a street near the Las Vegas Strip just after sunrise on Monday. Thousands were attending the music festival, Route 91 Harvest, when the shooting started. Hide Caption 3 of 30 Photos: Mass shooting at Las Vegas music festival People embrace outside the Thomas & Mack Center after the shooting. Hide Caption 4 of 30 Photos: Mass shooting at Las Vegas music festival Police arrive at the Sands Corporation plane hangar where some people ran to safety after the shooting. Hide Caption 5 of 30 Photos: Mass shooting at Las Vegas music festival A woman cries while hiding inside the Sands Corporation plane hangar. Hide Caption 6 of 30 Photos: Mass shooting at Las Vegas music festival Concertgoers dive over a fence to take cover from gunfire on Sunday night. Hide Caption 7 of 30 Photos: Mass shooting at Las Vegas music festival Police take position outside the Mandalay Bay. Hide Caption 8 of 30 Photos: Mass shooting at Las Vegas music festival A man lays on top of a woman as others flee the festival grounds. The woman reportedly got up from the scene. Hide Caption 9 of 30 Photos: Mass shooting at Las Vegas music festival Hide Caption 10 of 30 Photos: Mass shooting at Las Vegas music festival People are seen on the ground after the gunman opened fire. Hide Caption 11 of 30 Photos: Mass shooting at Las Vegas music festival People run from the festival grounds. Hide Caption 12 of 30 Photos: Mass shooting at Las Vegas music festival A woman is moved outside the Las Vegas Tropicana resort. Multiple victims were being transported to hospitals in the aftermath of the shooting. Hide Caption 13 of 30 Photos: Mass shooting at Las Vegas music festival People are searched by police at the Tropicana. Hide Caption 14 of 30 Photos: Mass shooting at Las Vegas music festival An ambulance leaves the intersection of Las Vegas Boulevard and Tropicana Avenue. Hide Caption 15 of 30 Photos: Mass shooting at Las Vegas music festival A man in a wheelchair is evacuated from the festival after gunfire was heard. Hide Caption 16 of 30 Photos: Mass shooting at Las Vegas music festival Victims of the shooting are tended to in the street. Hide Caption 17 of 30 Photos: Mass shooting at Las Vegas music festival Concertgoers help an injured person at the scene. Hide Caption 18 of 30 Photos: Mass shooting at Las Vegas music festival People gather around a victim outside the festival grounds. Hide Caption 19 of 30 Photos: Mass shooting at Las Vegas music festival A couple huddles after shots rang out at the festival. Hide Caption 20 of 30 Photos: Mass shooting at Las Vegas music festival An injured woman is helped at the Tropicana. Hide Caption 21 of 30 Photos: Mass shooting at Las Vegas music festival Police and emergency responders gather at the intersection of Las Vegas Boulevard and Tropicana Avenue. Hide Caption 22 of 30 Photos: Mass shooting at Las Vegas music festival A police officer takes position behind a truck. Hide Caption 23 of 30 Photos: Mass shooting at Las Vegas music festival A crowd takes cover at the festival grounds. Hide Caption 24 of 30 Photos: Mass shooting at Las Vegas music festival Police officers advise people to take cover in the wake of the shooting. Hide Caption 25 of 30 Photos: Mass shooting at Las Vegas music festival People tend to a victim at the festival grounds. Hide Caption 26 of 30 Photos: Mass shooting at Las Vegas music festival Police stand at the scene of the shooting. Hide Caption 27 of 30 Photos: Mass shooting at Las Vegas music festival A woman sits on a curb at the scene of the shooting. Hide Caption 28 of 30 Photos: Mass shooting at Las Vegas music festival Police are deployed to the scene. Hide Caption 29 of 30 Photos: Mass shooting at Las Vegas music festival A man makes a phone call as people run from the festival grounds. Hide Caption 30 of 30

But while some of the weapons were bought over the last 20 years, authorities believe 33 of the 47 guns -- most of them rifles -- were purchased between October 2016 and last month, an ATF spokesperson said

... at stores across the Southwest.

Paddock amassed at least some of his collection from a variety of gun stores throughout the southwestern US. He visited gun stores in Nevada, Utah, California and Texas, where he purchased rifles, pistols and shotguns, Snyder said

Chris Michel, the owner of Dixie GunWorx in St. George, Utah, remembered selling a gun to Paddock, he told CNN affiliate KTVX

"(Paddock) didn't set off any alarms. I didn't think there was a problem with him," Michel said. "He came in, he wanted a firearm, he knew exactly what he was looking for. He just wanted a shotgun."

He raised no red flags with authorities ...

There is no federal limit to how many firearms or how much ammunition someone can buy, and there's no national database that tracks gun purchases.

Federal law does require firearm dealers to conduct background checks on those purchasing weapons, which would check things like criminal history.

Several gun store owners Paddock purchased weapons from told CNN that no red flags were raised during his background checks.

"My staff takes their job very seriously and if there were any red flags during this transaction, like any other, it would be halted immediately," said David Famiglietti of New Frontier Armory in Las Vegas, where Paddock purchased a shotgun and a rifle this spring.

Richard Vasquez, the former chief of firearms technology for the ATF, said the fact that Paddock was able to purchase 33 guns should tell us "he had a very clean background."

"For a person to purchase 33 firearms -- and in different states -- there would be, in my opinion, absolutely no way it would have passed 33 checks if he had something in his background," Vasquez said.

Background checks for gun purchases are run against the National Instant Criminal Background Check System (NICS), developed by the FBI, that hits military, state and federal databases, as well as mental health records. Vasquez called it "a very comprehensive background check."

... though data on the kinds of purchases he made aren't kept.

Again, there's no national database that keeps track of gun purchases, but the ATF does require federal firearm licensees to report the purchase of multiple handguns by the same purchaser, as mandated by the Gun Control Act of 1968.

The sales "must be reported if they occur at the same time, or within five consecutive business days of each other," the ATF's website says.

Some states, such as California, regulate how often guns can be purchased. In that state, a buyer can only apply to buy a handgun once every 30 days . New York City takes that a step further, limiting purchases to once every 90 days, according to the Law Center to Prevent Gun Violence.

But Vasquez notes there's no equivalent federal requirement for reporting multiple purchases of long guns like rifles or assault weapons. That means the ATF and other law enforcement agencies never caught wind of Paddock's rifle purchases.