Dugway sheep incident The Dugway sheep incident , also known as the Skull Valley sheep kill , was a 1968 sheep kill that has been connected to United States Army chemical and biological warfare programs at Dugway Proving Ground in Utah . Six thousand sheep were killed on ranches near the base , and the popular explanation blamed Army testing of chemical weapon s for the incident , though alternative explanations have been offered . A report , commissioned by Air Force Press Officer Jesse Stay and first made public in 1998 , was called the " first documented admission " from the Army that a nerve agent killed the sheep at Skull Valley . Background . Since its founding in 1941 , much of the activity at Dugway Proving Ground is a closely guarded secret . Activities at Dugway included aerial nerve agent testing . According to reports from " New Scientist " , Dugway was still producing small quantities of anthrax as late as 1998 , 30 years after the United States renounced biological weapons . There were at least 1 , 100 other chemical tests at Dugway during the time period of the Dugway sheep incident . In total , almost of nerve agent were dispersed during open - air tests . There were also tests at Dugway with other weapons of mass destruction , including 328 open - air tests of biological weapons , 74 dirty bomb tests , and eight furnace heatings of nuclear material under open air conditions to simulate the dispersal of fallout in the case of meltdown of aeronautic nuclear reactors . Incident . In the days preceding the Dugway sheep incident the United States Army at Dugway Proving Ground conducted at least three separate operations involving nerve agents . All three operations occurred on March 13 , 1968 . One involved the test firing of a chemical artillery shell , another the burning of 160 U . S . gallon s ( 600 L ) of nerve agent in an open air pit and in the third a jet aircraft sprayed nerve agent in a target area about west of Skull Valley . It is the third event that is usually connected to the Skull Valley sheep kill . The incident log at Dugway Proving Ground indicated that the sheep incident began with a phone call on March 17 , 1968 at 12 : 30 a . m . The director of the University of Utah ' s ecological and epidemiological contract with Dugway , a Dr . Bode , phoned Keith Smart , the chief of the ecology and epidemiology branch at Dugway to report that 3 , 000 sheep were dead in the Skull Valley area . The initial report of the incident came to Bode from the manager of a Skull Valley livestock company . The sheep were grazing in an area about from the proving ground ; total sheep deaths of 6 , 000 - 6 , 400 were reported over the next several days as a result of the incident . The Dugway Safety Office ' s attempt to count the dead sheep compiled a total of 3 , 843 . Possible causes . Previously obtained documents said one such demonstration also occurred the day before the mysterious sheep deaths in 1968 . On 13 March 1968 , an F - 4 Phantom strike aircraft flew a test mission over the Dugway Proving Ground with chemical dispensers containing VX . One of the dispensers was not completely emptied during the test , and as the F - 4 gained altitude after its bombing run , VX trickled out in a trail behind the aircraft , drifted into Skull Valley , north of the proving ground , and settled over a huge flock of sheep . One explanation in the aftermath of the incident was that a chemical or biological agent had escaped from the Dugway Proving Ground . Circumstantial evidence seemed to support this assertion , the United States Army admitted to conducting open - air tests with the nerve agent VX in the days preceding the sheep kill . The Army intimated that a spray nozzle had malfunctioned during the test causing an aircraft to continue spraying VX as it climbed to higher altitudes . It was reported that a small amount of VX was found in the tissue of the dead sheep . Other information contradicted the initial assumptions about the cause of the incident . One contradiction to nerve agent exposure as a cause came in the symptoms of some of the sheep following the incident . Several sheep , still alive , sat unmoving on the ground . The sheep refused to eat , but exhibited normal breathing patterns and showed signs of internal hemorrhaging . Regular breathing and internal hemorrhaging are inconsistent with nerve agent exposure . Interesting is ; " . . . and in fact no other animals of any type , including cows , horses , dogs , rabbits , or birds , appeared to have suffered any ill effects , a circumstance that was hard to explain if VX had in fact causes the sheep deaths . " Aftermath . The incident had an impact on the Army , and U . S . military policy within a year . The international infamy of the incident contributed to President Richard Nixon ' s decision to ban all open - air chemical weapon testing in 1969 . The sheep incident was one of the events which helped contribute to a rise in public sentiment against the U . S . Army Chemical Corps during and after the Vietnam War . Ultimately , the Chemical Corps was almost disbanded as a result . Following the incident , the Army and other state and federal agencies compiled reports , some of which were later characterized as " studies " . A report which remained classified until 1978 and unreleased to the public until nearly 30 years after the incident was called the " first documented admission " by the Army that VX killed the sheep . In 1998 , Jim Woolf , reporting for " The Salt Lake Tribune " , made the content of the report public for the first time . The report described the evidence that nerve agent was the cause of the sheep kill as " incontrovertible . " The 1970 report , compiled by researchers at the U . S . Army ' s Edgewood Arsenal in Maryland , stated that VX was found in both snow and grass samples recovered from the area three weeks after the sheep incident . The report concluded that the " quantity of VX originally present was sufficient to account for the death of the sheep . " Even after the report surfaced the Army maintained that it did not accept responsibility for the incident nor did they admit negligence . As late as 1997 , one year before the report went public , U . S . Department of Defense officials stated that " the reason it ( the report ) was never published is because it wasn ' t particularly revealing . " Lee Davidson , Correspondent for Deseret News wrote in June 1994 that Ray Peck , who owned the sheep that were killed was outside working during the May 13 , 1968 , incident , and members of his family developed nervous - system illnesses for years afterwards , similar to ills reported by people exposed to low levels of VX in lab experiments . Also , the probe showed that medical tests the Army had used to claim humans were not affected are now considered inconclusive , and the Pecks had shown other signs of low - level VX exposure .