Details of the Port Adelaide player's death were emerging as teammates who were with him on the end of season trip returned to Australia.
McCarthy's body was found on a driveway at the Flamingo hotel and casino complex about 5.40am Sunday, Las Vegas time.
The 22-year-old had been separated from 10 teammates who were holidaying in the gambling mecca.
A group of Western Bulldogs players were also in Las Vegas, chaperoned by club runner and Victorian policeman Stuart Bailey, believed to be the first Australian to view McCarthy's body.
"Everything's leading towards an accident at this point of time," Bailey told reporters in Las Vegas on Tuesday (Wednesday, Australian time).
McCarthy is understood to have telephoned his girlfriend Danielle Smarrelli in Adelaide, sounding confused and saying he wanted to return home after being separated from his Port teammates.
"We know he was disorientated at the time through some phone calls he had with his girlfriend Danielle," Bailey said.
Investigators believe McCarthy walked into the Flamingo casino and took a lift to the third floor.
They believe he may have walked through at least two doors to the roof.
"He then walked to the edge," Bailey said.
"The evidence is suggesting that he has jumped off that wall to a palm tree, maybe been disorientated at how much the fall was, slipped and has fallen to the ground."
The Victorian-born player was holidaying with teammates Travis Boak, Matthew Broadbent, Alipate Carlile, Brett Ebert, Hamish Hartlett, Tom Logan, Andrew Moore, Paul Stewart, Jackson Trengove and Justin Westhoff.
The 10 Port players returned to Australia early Wednesday.
"The players are deeply shocked by the events and will be making no public comment," a Port Adelaide spokesman said.
The 10 players became separated from McCarthy in the early hours of Sunday, Las Vegas time.
Clark County Coroner Mike Murphy said McCarthy's body would be ready to be released on Wednesday, but it remains uncertain when he would be returned to Australia.
An autopsy has been performed but it could take up to 12 weeks for toxicology results, which McCarthy's family will decide whether to release to the public.
Port Adelaide's general manager (football) Peter Rohde travelled to Las Vegas to help repatriate McCarthy's body.
"Clearly we don't know exactly what has occurred, but we're starting to get a lot more information," Rohde told reporters in Las Vegas.
Port Adelaide chief executive officer Keith Thomas was expected to hold a media conference later on Wednesday in Adelaide.