Broker unresponsive after offer- contact owner?

[George G.]

My business partner and I have submitted an offer on an 8-unit building. The broker is super unresponsive and getting a hold of him is a losing game. The building is $500,000 and our offer was for $450,000. The property has been on the market for almost 8-9 months. 

The owner is 85 years old and has held the property for almost 30 years now. We feel our offer is competitive and have no problem offering more. 

How should we handle an unresponsive broker? Should we mail our offer to the owner directly to the legal mailing address?