Lombardo said he learned of the number through the Metropolitan Police Department forensics lab's work with the FBI on ballistics evidence from the shooting.
However, investigators still do not understand why Paddock stopped firing at the crowd across the street from his hotel. Lombardo told the Review-Journal that investigators found nearly 4,000 more rounds of unused ammunition in his hotel room.
Days after the shooting, Lombardo said a few of Paddock's weapons jammed. The sheriff reiterated that this week, but declined to give a specific number of weapons that jammed.
Lombardo and investigators still have not determined a motive for the shooting.
Lombardo also said FBI investigators are still speaking with Paddock's girlfriend, Marilou Danley. They interviewed her on Monday, but "nothing substantial was obtained," he told the Review-Journal.
The sheriff added that he will release more information on the shooting within two weeks. He also said he is "frustrated" with the ongoing spread of conspiracy theories about the shooting.
On the night of Oct. 1, Paddock fired at the crowd gathered for the Route 91 Harvest Country Music Festival across the street from the Mandalay Bay hotel. Over 500 people were injured and 58 people killed. About an hour after he began firing, Paddock was found dead in his hotel room.
It was the deadliest mass shooting in modern U.S. history.