MRCP2-2756

A group of politicians, all in their 50s, were attacked with an aerosol spray as they left a meeting. They presented to the Emergency department with symptoms of profuse tearing, eye pain, and corneal injuries. They also complained of shortness of breath, cough, and wheeze, and developed fever, nausea, and diarrhea within two hours of admission. One of the most severely affected patients had arterial blood gases showing hypoxemia and respiratory acidosis. Two of the patients eventually died despite maximal supportive care, while the other two required intubation and ventilation and had prolonged hospital stays. What was the likely substance present in the aerosol that caused this syndrome?