The major risks are extrapyramidal symptoms (EPS), dystonic reactions (which fall under EPS) and the development of tardive
dyskinesia. While it would be uncommon, there are some published reports that
tardive dyskinesia can develop after a single use. The other major concern is neuroleptic malignant syndrome (NMS). You can Google each of those to read about them.
It's difficult to speculate here, as you don't know what the dosage was, or what else it may have been combined with.