GMB and how to know if a competitor is writing negative reviews?

Is there anyway to work out who is leaving similar constant negative Google My Business reviews? We have a feeling a disgruntled ex employee (who was fired due to stealing) and leaving reviews to bring our rating down. I'm not a computer wizz, but maybe someone out there knows how to track the IP or knows if its possible?

Please note : We don't mind the odd negative review but this person we believe is going over the top and really trying to cause damage. Have contacted google but no reply/help.