An outside engineering firm will investigate what fair officials called the "freakish act of God" that brought down the main stage at the Indiana State Fair, killing five people and injuring 45 others.Indiana State Fair Commission Chairman Andre Lacy announced at an afternoon news conference that Thornton Tomasetti, a New York City-based international engineering company, had been retained to complete an internal investigation. Special Section: Indiana State Fair Stage Collapse "Our goal is to learn everything we can about why this tragedy occurred," he told reporters. "There isn't going to be any question that we aren't going to investigate. We will continue to ask the tough questions."Lacy said the company would review the stage structure, the rigging above the stage and how equipment was loaded onto the structure.Investigators arrived on site Monday and began their initial fact-finding investigation Tuesday, fair officials said.Scott Nacheman, a vice president in the company's Chicago office, said the process would likely be wrapped up by the end of the year.Thornton Tomasetti will then provide the State Fair Commission with a report of findings and recommendations, which officials said they will make public."We know that many are eager for answers today. We don't have them, and we won't speculate. It will take some time to reach conclusions," Lacy said.When pressed on the timeline of events Saturday night, fair spokesman Andy Klotz reiterated that at 8:45 p.m. an announcer told the crowd of 12,000 awaiting the Sugarland concert that severe weather was moving in and they could seek shelter in three nearby buildings.At the same time, fair officials were on their way to the stage to announce that the decision had been made to evacuate the grandstands, Klotz said, but the winds picked up first, bringing down the stage."This was a freakish act of God. I don't know how this could have been prevented," he said. "That decision (to evacuate or not), nobody's thinking about dollars. We are there to protect the public."The fair's severe weather policy stipulates that those in a tent structure should, "evacuate to a solid structure or building." A fund to help the victims and their families has been established by the Central Indiana Community Foundation. Donations can be made online or checks with Indiana State Fair Remembrance Fund in the memo line can be sent to CICF, Attn: Indiana State Fair Remembrance Fund at 615 N. Alabama St. Indianapolis, IN 46204.