Errors in the spotting system occur. I always suspect, that happens, when people switch sides, while spotting or something like that. Wherever it comes from, friendly vehicles appear with a red symbol. Happens sometimes. And if you see a kill message, with an american killing someone with a panther, it could have very well meant, that the tank exploded and bystanding infantry (or the leaving tank commander) got killed in the explosion, which was caused by an american destroying the tank.
If there is nobody else reporting this, it probably was coincidence. If not, than I am looking forward in reproducing this bug on a running server