Here’s what we know:
• Mr. Paddock was found dead on the 32nd floor of the Mandalay Bay Resort and Casino, the police said, and authorities believe he committed suicide.
• At least 10 guns were found in Mr. Paddock’s hotel room, including several rifles.
• Mr. Paddock was a resident of Mesquite, Nev., about 80 miles northeast of Las Vegas. Quinn Averett, a spokesman for the Mesquite police, said the department has had no previous contact with Mr. Paddock.
• The Las Vegas police also had nothing more than a routine traffic violation on Mr. Paddock, according to Kevin McMahill, the department’s undersheriff.
• The authorities searched Mr. Paddock’s home on Monday morning, finding guns and ammunition, Mr. Averett said.
• Sheriff Joseph Lombardo of the Las Vegas police called Mr. Paddock a “lone wolf” and said that it had not been evident that he was keeping weapons in his room, where he had been since Thursday. Employees who had been in his room had not noticed anything suspicious, the sheriff said.
• A companion of Mr. Paddock’s was questioned by the Las Vegas police but was not believed to have been involved in the shooting.
• The shooting began around 10:08 p.m. local time, the police said. The authorities estimated that 406 people were transported to hospitals. More than 22,000 people were at the concert.
• Mr. Paddock’s brother, Eric Paddock, told CBS that the suspect had owned several handguns and possibly a long gun, adding that he was “dumbfounded” by the shooting.
• He said that his brother sometimes gambled in Las Vegas and that he had last heard from him during Hurricane Irma, when the suspect checked in with relatives who lived in Florida.
• Mr. Paddock held additional property in northern Nevada that would be searched later Monday, the Las Vegas police said.
• He worked from 1985 to 1988 for a company that is now part of Lockheed Martin.
What we don’t know:
• The suspect’s motive is unclear.
• It is not yet clear whether the suspect planned the shooting alone or was working with others.
• The authorities have not announced whether the suspect had any ties to domestic or international terrorist groups.