What a weird way to try to poison someone. Mercury is really only poisonous under specific circumstances. Specifically, it is extremely dangerous to breath its vapors.
Touching it, or being near a small amount of it a few feet away really doesn’t do anything. It’s a safe-ish substance to make casual contact with (still not safe, but not profoundly noxious either).
There have been cases of people surviving drinking and even injecting mercury, as it isn’t toxic the way you might think it is under most circumstances.
It is still quite a dangerous thing, and using it maliciously (even if you have no idea what you’re doing) is no joke. Fortunately, the person targeted here is likely unaffected by mercury exposure.