How did actress Uma Thurman end up crashing into a tree at perhaps 40 miles per hour for the sake of a Quentin Tarantino movie?

Stunt professionals are starting to ask tough questions in the wake of the New York Times article in which Thurman revealed chilling footage of her violent crash while filming an iconic sequence in Mexico for 2004's Kill Bill Vol. 2. And Thurman's guild isn't happy either.

"The situation as it has been described sounds like a stunt and would be a likely safety violation," says a spokesperson for performers' union SAG-AFTRA, of which Thurman is a member. "In general, only stunt professionals should perform stunts with guidance from a stunt coordinator to ensure a correct and safe performance."

SAG-AFTRA doesn't have personnel to monitor on-set action around the country, let alone the world, and relies on actors to call its safety hotline at 844-SaferSet if they feel uneasy. In this case, Thurman apparently didn't alert the union. (Whether SAG-AFTRA will now investigate what happened seems unlikely given the passage of time and the lack of a complaint filed. The union didn't respond to a follow-up question.)

Thurman told the Times she didn't feel comfortable operating the car — which she described as a "deathbox" — and asked for a stunt driver to navigate the sandy road, but Tarantino refused in a fury because of the cost. (Tarantino countered: "I'm sure I wasn't in a rage.") In the video, Thurman is flung forward, and her head whips back over the seat, as the vintage convertible had neither shoulder belts nor headrests. Thurman said she suffered a concussion and damaged knees.

"The stuff that went on is appalling," says veteran stunt performer and coordinator Andy Armstrong. "That could have been a death by decapitation. The car could easily have rolled over [or] the camera could have flown forward. It was irresponsibility on a mega level."

Responsibility for Thurman's safety on set was shared by the producers, Tarantino and Keith Adams, the film's stunt coordinator. Lawrence Bender, the lead producer on Kill Bill, told THR on Wednesday, "I deeply regret that Uma suffered the pain she has, both physically and emotionally, for all of these years from the accident that occurred on the set of Kill Bill. I never hid anything from Uma or anyone else nor did I participate in any cover-up of any kind— and I never would."

In addition, THR reported that Bender has said privately he believes there was no wrongdoing on the set and that he had reviewed the 2004 incident with key crewmembers to double check.

On movies made under Directors Guild of America jurisdiction, the first assistant director also has responsibility for safety. But a source with knowledge of the matter says Kill Bill was not a DGA movie, as it was made before Tarantino joined the guild. Meanwhile, the Producers Guild of America, which sounds like a union but isn't, has no authority over what happens on set. Workplace safety regulators at Cal-OSHA would have had jurisdiction had the accident occurred in California, but it didn't — and so far, it appears, no one filed a complaint or report of the incident with any government agency in California or Mexico.

Armstrong says stunt coordinator Adams, whose job includes vetoing unsafe action, could have stepped in to prevent Thurman from driving the car, but he wasn't on set at the time. "The stunt coordinator was told to stay in his hotel that day, stay home," says Armstrong, who adds that he knows this because he has spoken to Adams about the matter. Armstrong notes that Adams has particular expertise in automotive stunts. Voice and email messages for Adams were not returned.

Tarantino has also claimed that the stretch of road was straight when traveled in one direction but had a curve when traversed the opposite way. "I thought a straight road is a straight road, and I didn't think I needed to run the road again to make sure there wasn't any difference going in the opposite direction," he said. But Armstrong says the geometry-defying notion that a curve only existed when traversed in a particular direction is absurd.

And Melissa Stubbs, another veteran stunt performer and coordinator, notes that even if Thurman agreed to drive the car, it's not her responsibility to say no and make it stick. "That's why you need an experienced stunt coordinator," she says.

Kim Masters and Chris Gardner contributed reporting.