US investigators are trying to piece together the cause behind Sunday’s massacre at a country music festival in Las Vegas that left 58 people dead and hundreds more wounded.

The gunman responsible for the deadliest mass shooting in modern US history meticulously planned the event and spent decades acquiring weapons.

Police say that the 64-year-old shooter, Stephen Paddock, never roused suspicion before the incident as he lived a secret life.

But as more details emerge about the gunman so do more questions as to how he pulled off his attack.

TRT World’s Harry Horton reports.