Las Vegas authorities are standing by their timeline of the deadliest shooting in modern US history despite it being disputed by the hotel where the gunman opened fire.
Sheriff Joseph Lombardo told reporters on Friday that Stephen Paddock rained down bullets on a folk festival concert crowd starting at 10.05pm on October. 1, killing 58 people.
Six minutes earlier, he said Paddock sprayed 200 rounds from his Mandalay Bay room into the hallway, hitting a security guard in the leg.
That timeline released earlier this week differed from a week ago, when authorities said the guard was shot after Paddock opened fire on the crowd.
The changes led to questions about why police and hotel security weren't able to stop Paddock sooner.
Mr Lombardo hit back at criticism over the timeline, saying he was "absolutely offended" over any suggestion that authorities bungled the response.
Mandalay Bay officials have disputed whether six minutes actually passed between the first gunfire in the hallway and the start of the concert rampage.
Mr Lombardo also revealed that a post-mortem examination showed Paddock had no visual abnormalities in his brain but that it was sent to a facility to look for any minute problems.
Authorities have not determined why Paddock carried out the massacre before shooting himself. Some believed a post-mortem could shed light on any medical problems that could have contributed.
FBI Special Agent in Charge Aaron Rouse said investigators have found no signs that Paddock had ideologies or connections to any groups.