In 1958 one of his mechanical assemblages "attacked" a woman at the San Francisco Museum of Modern Art's annual Christmas party and holiday exhibition. His "Xmas Tree" was "sort of the pinnacle of the kinetic junk sculptures because I'd never attempted anything so complicated", built out of "two radios, two phonographs, flashing lights, electric fans, saw motor--all controlled by timers, hooked so would cycle all these things." One of the record players played "I Hate to See Christmas Come Around". At the opening, which Hedrick refused to attend, he set a timer so that the piece "suddenly began flashing its lights, honking its horns, and playing its records." One woman who was standing next to the piece when it suddenly turned on found her fur coat tangled in it and then received an electrical shock. "It caused quite a sensation not because of its artistic merit, but because it attacked this lady, which I thought was very nice... I wasn't making it as an art thing. I was more interested in making a "thing", and if it attacked people—well I guess I knew it was going to attack...I knew it would probably attack because I laid the trap. So it entertained me; I thought the evening was a success."