Berkeley building inspectors have been on the scene from the moment they heard about the tragedy, trying to protect other residents who could be in danger and trying to figure out what happened.
PHOTOS: Six killed in balcony collapse in Berkeley
To get to the bottom of this, the ABC7 News I-Team placed several public records requests for police reports, inspection documents and more.
Berkeley officials say it will be days or perhaps weeks before we see that information, but one long-time engineer says he knows exactly what happened and why.
Gene St. Onge has been a civil structural engineer for 37 years and he says it's clear what happened.
"The main, if not the only, cause of the problem is dry rot of the material, which is caused by water intrusion," he said.
READ MORE: A look at past US accidents involving balcony collapses
St. Onge said when a deck gives way due to dry rot, it doesn't just snap and fall - it bends before the break.
"This kept rotating like this, until the stress was too much and then it just seemed to flip," St. Onge said.
That explains why the balcony landed upside down on the deck below, throwing the victims onto the sidewalk and street.
RAW VIDEO: Berkeley officials held press conference about balcony collapse
At the news conference on Tuesday, building officials revealed that the project fell under the 1998 guidelines of 60 pounds per square-foot.
St. Onge said this deck should have easily held all those young people at the party.
"I considered 14 people at an average of about 150 pounds. That came out to a little over 40 pounds per square-foot, which is well within the design load for which they should have been designed at the time," he said.
Dry rot was also responsible for a deck collapse in San Francisco during a cocktail party in February 1996. One woman lost her life and 14 others were injured.
The I-Team is hoping to speak with the construction company about their work. This building is not very old, finished just eight years ago.
A crane is now in place- looks like they will soon make first attempts to get near the Berkeley Balcony that fell. pic.twitter.com/rpCaO1BuHE— Amy Hollyfield (@amyhollyfield) June 16, 2015
Andrea Gainford of Wexford heard the sirens following balcony collapse. Then texts came in from family in Ireland. pic.twitter.com/HSg2W5SLHG— Lyanne Melendez (@LyanneMelendez) June 16, 2015
Memorial where 6 people died overnight after a balcony in Berkeley collapsed. Victims were celebrating a 21st b-day. pic.twitter.com/bSEuVqvuOj— Amy Hollyfield (@amyhollyfield) June 16, 2015