-- Tannerite and ammonium nitrate -- explosive materials -- were found among the suspected Las Vegas gunman's arsenal of weapons and ammunition spread across a number of locations.
Suspected shooter Stephen Paddock, 64, opened fire on concertgoers from the 32nd floor of the Mandalay Bay Resort and Casino, killing 59 people and injuring hundreds more. In the hotel room, police found at least 23 handguns and rifles, some with scopes. Ammunition and more than 10 suitcases were found in the room, police said. Police also found 19 additional firearms, Tannerite, and some 1,000 rounds of ammunition at Paddock's home in Mesquite, while ammonium nitrate was found in his car.
Here's what you need to know about the explosive materials.
What is Tannerite?
Tannerite is the brand name for an explosive often used for target practice, which can be purchased in many sporting goods stores or online. It is known as a "binary exploding target," which creates an explosion when fired upon. It's sold as a "shot-indicator" and is initiated when shot at.
Tannerite falls under the same federal laws as black powder and all other explosives that are exempt for sporting use, according to the company.
"Remember though, just because it's a legal product under federal law if used as prescribed, does not mean that you can use it in any manner you wish," the Tannerite website cautions.
Binary explosives are pre-packaged products consisting of two separate components, usually an oxidizer like ammonium nitrate and a fuel such as aluminum or another metal, according to the Bureau of Alcohol Tobacco, Firearms and Explosives (ATF). Separately, these components do not meet the definition of "explosives," according to ATF. When sold separately, ATF does not regulate the sale and distribution of these component chemicals.
"However, when the binary components are combined, the resulting mixture is an explosive material subject to the regulatory requirements," according to ATF.
"In light of the tragedy that our great nation has suffered in Las Vegas, Tannerite® Sports L.L.C. sends our thoughts and prayers to the victims and their families during this trying time and the ones to follow in the future due to this horrific event. In addition, we send our thoughts and prayers to the first responders and the people of Las Vegas who also have suffered this tragedy and are helping overcome the difficulties from it," said the Tannerite company in a statement in response to the mass shooting in Las Vegas.
One of the bombs used in the Chelsea bombing in New York City last year was found with a label on it for Tannerite.
What's ammonium nitrate?
Ammonium nitrate is a chemical often used as a fertilizer in agriculture production. However, the chemical is also used as a component for explosive mixtures used commercially, such as in mining.
Incidents involving ammonium nitrate are rare, given that the United States uses millions of tons of it annually, yet they can have "severe consequences," according to an Environmental Protection Agency report.
Explosions of stored ammonium nitrate are responsible for some of the worst chemical disasters on record, reads the report.
For example, on April 17, 2013, a fire at an ammonium nitrate storage facility in West, Texas, killed 15 people, including some of the firefighters responding to the fire and more than 250 people were injured. Extensive damage was caused to the surrounding area.
The Department of Homeland Security runs the Ammonium Nitrate Security Program, which was developed in response to direction from Congress to "regulate the sale and transfer of ammonium nitrate by an ammonium nitrate facility ... to prevent the misappropriation or use of ammonium nitrate in an act of terrorism."
The program seeks to reduce the likelihood of a terrorist attack involving misused ammonium nitrate by creating a registration program for purchasers and sellers of ammonium nitrate, according to DHS.
Additional information on Paddock's use of the chemical was not immediately known.