It could be a concentrated dose of dimethyl mercury, a chemical which easily absorbs thru the skin and kills instantly. A chemistry professor from a university in California had something like 1/1000 of a drop go thru her latex gloves(yeah! She was wearing gloves and they didn't didn't help her). The drop fell on her gloved hand and rolled off onto the floor. She knew how dangerous it was so she immediately went to the E.R. But they couldn't help her. She died a day later. The report didn't indicate the symptoms so we really can't say for sure.
There are so many aerosols that can kill a person. But here's a clue. There's a movie out there with a scene where someone is instructing a doctor on killing a dictator. This person tells the doctor that the stethoscope has a chemical on it and that all the doctor has to do it press it against the dictator's skin and he'll die immediately. I think the movie is Spy Game.
The Jackal is my favorite Bruce Willis movie. He's actually scary in that movie. And his techniques are ingenious. I've seen it a hundred times. What I've always wondered was whether the Jackal was gay, or just making a backup plan when he seduced that man.