The Las Vegas concert massacre was clearly methodically planned, according to a world-famous forensic scientist from southern Connecticut, who weighed in on the case Thursday.

Henry Lee isn't working on the Vegas case, which left 58 concertgoers dead and hundreds more wounded, but he's investigated a number of mass shootings and consulted on high-profile slayings around the country.

Lee says the number of weapons Stephen Paddock brought to the Mandalay Bay hotel, the tools he used to break hotel windows before opening fire on concertgoers and the cameras he set up in the hallway to monitor for police all point to a premeditated attack.

But what's less obvious, he says, is why investigators haven't determined a motive -- although mass murderers generally have similar motives. One is going out with a bang.

It's also anomalous because Paddock was 64 years old, far older than most mass killers.

Lee says investigators will also focus on Paddock's financial records, computers, and cellphone as they try to piece together what is expected to be a long investigation.

In a revised timeline of events, police now say Paddock shot the security guard before he opened fire on concertgoers -- not during the rampage as they previously stated.