Liam PayneA hotel guest attending the CasaSur Palermo in Buenos Aires for his wedding witnessed the fatal fall and is haunted by what he saw.

Bret Watson was in a room on the first floor of the hotel with his wedding planner and when they looked out the window they saw Liam in free fall. Bret appears in our new documentary, TMZ Presents: Liam Payne: Who’s to Blame? airing tonight at 8pm ET on FOX and streaming on Hulu starting Tuesday.

Bret and the wedding planner ran to the balcony, looked down… and immediately identified Liam, who he believes died instantly.

Bret says that the sound of Liam’s body hitting the ground was even more powerful than the fall itself, and from the interview it’s clear that he’s still having some pretty serious emotional difficulties.

Bret and the wedding guests saw Liam throughout the day and noticed that he was becoming increasingly drunk and erratic as the hours went by. Bret saw the hotel staff’s last encounter with Liam as they carried him by his arms and legs from the lobby to his room, where they left him alone. A short time later Liam fell from the balcony.

Bret’s account is very different from that of Liam’s good friend Roger Noreswhom the public prosecutor wants to charge with abandonment. Nores insists When he left Liam for the last time, an hour before Fall, the singer was in a good mood and just a little tipsy.

According to official documents obtained by TMZ, the timeline shows Liam was looking for cocaine early in the day … even when he texted Nores, he needed 6 grams.

Braian Paiz, a waiter whom prosecutors want to charge with supplying drugs to Liam, tells us that he visited Liam twice during his stay Drink whiskey and do cocainewhich Paiz delivered. He insists Liam didn’t pay him for the drugs.