And now we have more on the mystery of that death on the roller coaster in texas. You saw the headlines this weekend and tonight abc's clayton sandell decided to ask engineers who design these rides... See More
And now we have more on the mystery of that death on the roller coaster in texas. You saw the headlines this weekend and tonight abc's clayton sandell decided to ask engineers who design these rides how they test roller coasters before you get on board. Reporter: Tonight the texas giant is quiet, shut down after 52-year-old mother rosey esparza on her first visit to six flags over texas fell and died. She goes up like this and then when it drops to come down, that's when it released and she just tumbled. Reporter: Witnesses say she fell early in the ride during a steep turn. Family riding with her, including a son enduring an agonizing wait for the ride to end. He said let me go down there and find my brown. Reporter: Before the freak accident here, esparza expressed concern to a park employee that her safety restraint, in this case, a t-shaped lap bar was not secure. On a conference call today, the six flags ceo would not speculate. Experts are investigating the cause of the accident. Reporter: Summer is prime coaster season. I'm a very anxious person. I don't know if I'm going to get on. Reporter: Statistically deaths are extremely rare, one in 750 million people. Jim is a coaster design guru. Computer models, backup safety systems and years of testing is supposed to make them thrilling but safe. For example, if all the coasters safety bars aren't closed properly, the ride shouldn't go. I am extremely confident the design process is so sophisticated that I feel like when I go on a ride it's a safe attraction to be on. Reporter: Why she fell is a histry but because there was no sign of foul play the accident will not be investigated by a federal or state agency. It's up to six flags to investigate itself. Clayton sandell, abc news, texas.
This transcript has been automatically generated and may not be 100% accurate.