"I'm frustrated", Joseph Lombardo, the Las Vegas sheriff, said at a news briefing.
"This individual purposely hid his actions leading up to this event, and it is hard for us to find the answers", said Lombardo, who said he was frustrated with the speed of the investigation.
Stephen Paddock, 64-year-old wealthy former accountant and high-stakes gambler has been identified by police as the man behind the deadliest mass shooting in modern USA history when he opened fire from the Mandalay By Hotel and Casino on October 1, killing 58 people and injuring almost 500 others, before turning the gun on himself as police closed in.
In the CBS interview images of Paddock's body were shown and the officers described finding his body after blowing open the bullet-hole ridden doorway to his room.
Lombardo said a small team of Las Vegas police officers - two K-9 officers, a detective and a SWAT team member -converged on the Mandalay Bay Hotel and minutes later, they breached the gunman's hotel room door on the 32nd floor.
Even as the gunman began firing on the crowd below - shooting for 10 minutes - police were not aware that the security guard was shot until they arrived on the hotel's 32nd floor. The sheriff added that a complete evaluation of Paddock's mental condition was not yet done.
Russian jet crashes in Syria, crew killed
Photo taken on October 21, 2015 shows a Russian Sukhoi Su-24 taking off from the Hmeimim airbase in the Latakia province, Syria. The Su-24 has a side-by-side seating arrangement, usually consisting of a pilot and a weapon system operator.
Lombardo declined to reveal what they've said, but he stated, "Every piece of information we get is one more piece of the puzzle". "We believe he chose to take the lives he did and he had a very purposeful plan that he carried out".
"I think they prevented a thousand deaths, and I think it's important for the American public to understand that", Lombardo said on Sunday.
The Las Vegas Review-Journal reports (http://bit.ly/2yzrWEz) that Eric Paddock arrived in town Saturday for hours of interviews with Federal Bureau of Investigation agents, a police detective, a profiler and a psychologist.
"So, he had that written down and figured out so he would know where to shoot to hit his targets from there". Authorities so far have struggled to find a motive.
Authorities are still working to determine the shooter's motives, which still remain largely a mystery a week after the massacre. "I just threw them in the casino", Donaldson said. "You know, we were still clearing that room, the curtains, moving the curtains", Matthew Donaldson explained. "It just looked like nearly a gun store", he said. "So many magazines. Stacks and stacks of magazines everywhere".
Authorities also said Monday that Paddock targeted aviation fuel tanks, stocked his vehicle with explosives and had personal protection gear as part of an escape plan.