Speaking of his "Twilight Zone: The Movie" segment, I'd never heard this story before (from Wiki):
During the filming of the "Time Out" segment directed by Landis on July 23, 1982, at around 2:30 a.m., actor Vic Morrow and child actors Myca Dinh Le (age 7) and Renee Shin-Yi Chen (Chinese: 陳欣怡; pinyin: Chén Xīnyí, age 6) died in an accident involving a helicopter being used on the set. The two child actors were hired in violation of California law, which prohibits child actors from working at night or in proximity to explosions, and requires the presence of a teacher or social worker. During the subsequent trial, the illegality of the children's hiring was admitted by the defense, with Landis admitting culpability for that (but not the accident), and admitting that their hiring was "wrong".
In the scene that served as the original ending, Morrow's character was to have traveled back through time again and stumbled into a deserted Vietnamese village where he finds two young Vietnamese children left behind when a U.S. Army helicopter appears and begins shooting at them. Morrow was to take both children under his arms and escape out of the village as the hovering helicopter destroyed the village with multiple explosions which would have led to his character's redemption. The helicopter pilot had trouble navigating through the fireballs created by pyrotechnic effects for the sequence. A technician on the ground did not know this and detonated two of the pyrotechnic charges close together. The flash-force of the two explosions caused the low-flying helicopter to spin out of control and crash land on top of Morrow and the two children as they were crossing a small pond away from the village mock-up. All three were killed instantly; Morrow and Le were decapitated by the helicopter's top rotor blades while Chen was crushed to death by one of the struts. A report released in May 1984 by the National Transportation Safety Board stated: