output correct JSON response

I'm using apex language, which is similar to JAVA to generate some JSON output with the following code:

    generator = JSON.createGenerator(true);
    generator.writeStartObject();
    generator.writeFieldName('employees');
    generator.writeStartArray();
    for(User u : getUsers()) {
        generator.writeStartObject();
        generator.writeStringField('key', u.Id);
        generator.writeStringField('nickname', u.CommunityNickname);
        generator.writeStringField('lastname', u.LastName);
        if(u.Region__c != null) {
            generator.writeStringField('region', u.Region__c);
        }
        else {
            generator.writeStringField('region', '');
        }
        if(u.Home_District__c != null) {
            generator.writeStringField('district', u.Home_District__c);
        }
        else {
            generator.writeStringField('district', '');
        }
        if(u.Home_District__c != null) {
            generator.writeStringField('pack', u.Pack__c);
        }
        else {
            generator.writeStringField('pack', '');
        }
        generator.writeStringField('employee', u.Name);
        generator.writeEndObject();
    }
    generator.writeEndArray();
    generator.writeFieldName('events');
    generator.writeStartArray();
    for(Site_Visit__c sv : getSiteVisits()) {
        generator.writeStartObject();
        if(sv.Status__c.toLowercase() == 'scheduled') {
            generator.writeFieldName('assigned');
            generator.writeStartObject();
            if(sv.Intended_Start_Date_Time__c != null) generator.writeStringField('start_date', String.valueOf(sv.Intended_Start_Date_Time__c));    
            if(sv.Estimated_Completion_Date_Time__c != null) generator.writeStringField('end_date', String.valueOf(sv.Estimated_Completion_Date_Time__c));
            generator.writeStringField('text', String.valueOf(sv.Name));
            if(sv.Assigned_Employee__c != null) generator.writeStringField('section_id', String.valueOf(sv.Assigned_Employee__c));
            generator.writeStringField('id', String.valueOf(sv.Id));
            generator.writeStringField('color', String.valueOf('#ffffff'));
            generator.writeStringField('textColor', String.valueOf('#000000'));
            generator.writeEndObject(); 
        }
        if(sv.Status__c.toLowercase() == 'unassigned') {
            generator.writeFieldName('unassigned'); 
            generator.writeStartObject();
            if(sv.Intended_Start_Date_Time__c != null) generator.writeStringField('start_date', String.valueOf(sv.Intended_Start_Date_Time__c));    
            if(sv.Estimated_Completion_Date_Time__c != null) generator.writeStringField('end_date', String.valueOf(sv.Estimated_Completion_Date_Time__c));
            generator.writeStringField('text', String.valueOf(sv.Name));
            generator.writeStringField('id', String.valueOf(sv.Id));
            generator.writeStringField('color', String.valueOf('#ffffff'));
            generator.writeStringField('textColor', String.valueOf('#000000'));
            generator.writeStringField('woNumber', String.valueOf(sv.Work_Order__r.Name));
            generator.writeStringField('woType', String.valueOf(sv.Work_Order__r.Work_Order_Type__c));
            generator.writeStringField('customer', String.valueOf(sv.Work_Order__r.Customer__c));
            generator.writeEndObject();             
        }
        generator.writeEndObject(); 
    }
    generator.writeEndArray();
    generator.writeEndObject();

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The current output is like the following:

{
employees:
    employee
    employee
events:
    unassigned:
        event
    unassigned:
        event
    assigned:
        event
    assigned:
        event
    (empty object?)
    (empty object?)
}

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I need it to be like this:

{
employees:
    employee
    employee
events:
    unassigned:
        event
        event
    assigned:
        event
        event
}

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Events should be an object (not an array) that has two fields: assigned and unassigned. Each of those fields is an array of events that match their description.  How can I modify the existing structure to get the correct output.

Thanks for any help.