They have no duty to respond, legally.
You may be able to back that up some way, but if an officer has the ability to respond to a felony in progress, and fails to do so, I think that officer should be subject to being fired, and possibly prosecuted. If lives are on the line, all the more so. If someone died because he simply took a pass on helping, I’d consider him as guilty as the person who did the killing.
I sure wouldn’t want to work beside him. He would have just shown me that he could not be counted on if something similar involved me.