Almost certainly yes, although I can't think of any examples off-hand. I would expect that some trilobites may have also eaten smaller sea scorpions, or larger ones that had already died.

Unfortunately, catching animals in the act like that is really quite difficult in the fossil record. We can get fossilized excrement that contains trilobite fragments, so we know something was eating them, but we don't know what animal the fossil feces came from. As for a sea scorpion with a trilobite in its claw or something like that, the sea scorpion would have to have been buried alive in an undersea mudslide or a fall of volcanic ash or something like that while it was working on the trilobite - and under those circumstances, it would probably let go and try to save itself from being buried and killed than be worried about eating the trilobite.