Police said the suspect is in his 70s and may have lived in the residence with the victims but did not identify him or the victims.
A 19-year-old man who was expelled from high school for disciplinary reasons returned to the building in Parkland, Florida and opened fire on February 14, 2018, killing at least 17 people.
No official figure exists for the number of guns but there are thought to be about 300 million in the US, held by about a third of the population.
Federal agents have spent the week collecting evidence amid the thousands of items that were abandoned in panic, some of them stained with blood.
The piece of paper was found by police officers who stormed Paddock's room after he launched his attack from Mandalay Bay hotel.
Stephen Paddock had booked two rooms at Chicago's Blackstone hotel overlooking an expansive downtown park where the popular Lollapalooza music festival took place over four days in August.
Stephen Paddock, the man who killed 59 concert-goers in Las Vegas was 64 years old, much older than the other mass shooters of recent infamy, all of whom were less than 30 years old.
President Donald Trump arrived Wednesday in Las Vegas to meet survivors of the deadliest mass shooting in modern US history.
Popular American late-night TV shows address the Las Vegas shooting, and questions leaders why they continue to allow it to happen.
Express at Ground Zero: Did lax Mandalay Bay hotel security give Las Vegas gunman a deadly shot in the arm?
For an Indian who came to Vegas a week back, the lapses in security measures were as plain as day.
The gunman was identified as Stephen Craig Paddock, who had checked into the hotel room on 28 September.
Stephen Craig Paddock was a retired accountant who lived on a desert golf course in Mesquite Nevada, with no known history of violence.