Authorities found explosives, as well as 18 guns and thousands of rounds of ammunition at suspected Las Vegas shooter Stephen Paddock’s home, police said Monday evening. Ammonium nitrate—a chemical compound that can be used in explosives—was found in Paddock’s car. Officials say Paddock also had “bump-stock” devices that he may have added to increase the rate of fire on his weapons. The devices, which have faced increasing calls for restrictions in recent years, convert semi-automatic weapons into automatic ones. Paddock is accused of opening fire on a country-music festival from his hotel window Sunday evening, killing at least 59 people and injuring over 500 others. Previously Monday, officials discovered about 20 rifles and handguns in Paddock’s hotel room. The weapons reportedly included AR-15-style and AK-47-style rifles, and two guns that had been modified to be fully automatic. Two of the guns were reportedly mounted on tripods. Police also found a large stockpile of ammunition.