Authorities who are investigating the mass shooting  in Las Vegas on Oct. 1 have again altered the timeline of events that took place during the deadly rampage, citing what they call a "human entry" that caused their initial assessment to be incorrect.

Clark County Sheriff Joe Lombardo addressed reporters at a press conference in Las Vegas on Friday (Oct. 13), revealing that while the ongoing investigation has yielded no tangible motive for the crime, authorities do have a clearer picture of how events unfolded the night 64-year-old Stephen Paddock opened fire on the crowd during the final night of the Route 91 Harvest Festival in Las Vegas.

The initial investigation revealed that Paddock had carefully planned the shooting to the point of posting cameras in the hall to warn him when police approached, and he used that warning system to shoot through the door and wound a security guard who approached his room. Police initially believed that shooting took place six minutes before Paddock opened fire on the crowd, killing at least 58 people and wounding more than 500 others in the worst mass shooting in modern American history.

That six-minute gap gave rise to speculation about why police didn't make it to Paddock's room in time to knock down the door and prevent the shootings, according to CNN, but at Friday's news briefing, Lombardo said new information has revealed that Paddock shot the security guard right around the same time he began firing into the crowd. The original timeline estimated that Paddock shot the security guard at 9:59PM and opened fire on the crowd six minutes later, while the revised timeline states that he shot the security guard through the door at around 10:05, right around the time his shooting spree into the crowd began.

Las Vegas Survivors Memorialize Shooting With Powerful Tattoos

According to CNN, the security guard arrived near Paddock's room via the stairs at 9:59, but Paddock had screwed the door to the stairwell shut, forcing the guard to go to an upper floor and come back down to Paddock's room by a circuitous route that took him until 10:05. According to reporting, it appears the security guard was on routine rounds and had not been attracted by anything untoward in regard to Paddock until he found the door inaccessible.

Lombardo attributed the erroneous time of 9:59 to a "human entry" in a security log that has been disproven, a position echoed by MGM Resorts International, which owns the Mandalay Bay hotel from which Paddock conducted his crime. MGM states that time reference "was derived from a Mandalay Bay report manually created after the fact without the benefit of information we now have. We are now confident that the time stated in this report is not accurate."

Sheriff Lombardo said he is "absolutely offended" by the characterization that the investigation into the crime has been incompetent. CNN's reporting pushes back at his comments a bit, saying, "The lack of answers, especially about the timeline, seems all the more curious when, it would appear, many moments in the shooter's dayslong preparation -- and the actual assault -- were captured by hotel video surveillance or by cameras the gunman himself installed in his suite and hallway outside."

Lombardo says it's likely more facts of that night are yet to be reported, calling the shooting "a very dynamic event."

Three survivors of the Vegas shooting have filed a lawsuit against the manufacturer of the bump stock devices that allowed Paddock to fire semi-automatic weapons like automatic weapons, and another shooting victim has filed suit against the hotel and Route 91 concert promoter Live Nation, claiming negligence in not adequately training staff to deal with the possibility of such an emergency.

Photos From the Route 91 Shooting Show Kindness Amidst Chaos

Country Singers Are Praying for Vegas

More From News/Talk 95.1 & 790 KFYO