public class WSController {
    public List<String> un {get;set;}
    public List<String> pn {get;set;}
    public List<String> dmutc {get;set;}

    String jsonStr = '{"DateModifiedUtc":"2016-09-07T20:12:47.1519119Z",' +
'"AgentInfoList":[{"Username":"Agent00@gmail.com","PriorityNumber":0}, ' +
'{"Username":"Agent01@gmail.com","PriorityNumber":0},{"Username":"Agent02@gmail.com","PriorityNumber":0},' +
'{"Username":"Agent03@gmail.com","PriorityNumber":0},{"Username":"Agent04@gmail.com","PriorityNumber":0},' +
'{"Username":"Agent05@gmail.com","PriorityNumber":0},{"Username":"Agent06@gmail.com","PriorityNumber":0},' +
'{"Username":"Agent07@gmail.com","PriorityNumber":0},{"Username":"Agent08@gmail.com","PriorityNumber":0},' +
'{"Username":"Agent09@gmail.com","PriorityNumber":0},{"Username":"Agent10@gmail.com","PriorityNumber":0},' +
'{"Username":"Agent11@gmail.com","PriorityNumber":0},{"Username":"Agent00@gmail.com","PriorityNumber":1},' +
'{"Username":"Agent01@gmail.com","PriorityNumber":1},{"Username":"Agent02@gmail.com","PriorityNumber":1},' +
'{"Username":"Agent03@gmail.com","PriorityNumber":1},{"Username":"Agent04@gmail.com","PriorityNumber":1},' +
'{"Username":"Agent05@gmail.com","PriorityNumber":1},{"Username":"Agent06@gmail.com","PriorityNumber":1},' +
'{"Username":"Agent07@gmail.com","PriorityNumber":1},{"Username":"Agent08@gmail.com","PriorityNumber":1},' +
'{"Username":"Agent09@gmail.com","PriorityNumber":1},{"Username":"Agent10@gmail.com","PriorityNumber":1},' +
'{"Username":"Agent11@gmail.com","PriorityNumber":1},{"Username":"Agent00@gmail.com","PriorityNumber":2},' +
'{"Username":"Agent01@gmail.com","PriorityNumber":2},{"Username":"Agent02@gmail.com","PriorityNumber":2},' +
'{"Username":"Agent03@gmail.com","PriorityNumber":2},{"Username":"Agent04@gmail.com","PriorityNumber":2},' +
'{"Username":"Agent05@gmail.com","PriorityNumber":2},{"Username":"Agent06@gmail.com","PriorityNumber":2},' +
'{"Username":"Agent07@gmail.com","PriorityNumber":2},{"Username":"Agent08@gmail.com","PriorityNumber":2},' +
'{"Username":"Agent09@gmail.com","PriorityNumber":2},{"Username":"Agent10@gmail.com","PriorityNumber":2},' +
'{"Username":"Agent11@gmail.com","PriorityNumber":2}]}';


// Parse entire JSON response.
    public List <String> WSController() {
        //Returns the token that the parser currently points to
        parser = JSON.createParser(jsonStr);
        if (parser.nextToken() != null)
        {
            while ((parser.getCurrentToken() == JSONToken.FIELD_NAME) && (parser.getText() == 'Username'))
            {
                fieldName = parser.getText();
                //returns the value of the next token
                parser.nextToken();
                un.add(parser.getText());
                system.debug('this is the Username list: ' + un);
            }
            while ((parser.getCurrentToken() == JSONToken.FIELD_NAME) && (parser.getText() == 'PriorityNumber'))
            {
                fieldName = parser.getText();
                //returns the value of the next token
                parser.nextToken();
                pn.add(parser.getText());
                system.debug('this is the Priority Number list: ' + pn);
            }
            while ((parser.getCurrentToken() == JSONToken.FIELD_NAME) && (parser.getText() == 'DateModifiedUtc'))
            {
                fieldName = parser.getText();
                //returns the value of the next token
                parser.nextToken();
                dmutc.add(parser.getText());
                system.debug('this is the Date Modified: ' + dmutc);
            }
        }
        return pn;
    }

    //wrapper class
    public class JSON2Apex
    {
        public String DateModifiedUtc;
        public List<AgentInfoList> AgentInfoList;
    }
    public class AgentInfoList
   {
        public String Username;
        public Integer PriorityNumber;
    }
    public static JSON2Apex parse(String json)
    {
        return (JSON2Apex) System.JSON.deserialize(json, JSON2Apex.class);
    }

    JSON2Apex myParsedResult = JSON2Apex.parse(jsonStr);

    public void myMethod(){
        for (AgentInfoList agentItem : myParsedResult){
            un = agentItem.Username;
            pn = agentItem.PriorityNumber;
        }
    }

}

for (AgentInfoList agentItem : myParsedResult.AgentInfoList){
        un.add(agentItem.Username);
        pn.add(agentItem.PriorityNumber);
  }

public class WSController {
    public JSON2Apex info { get; set; }

    String jsonStr = '{"DateModifiedUtc":"2016-09-07T20:12:47.1519119Z",' +
'"AgentInfoList":[{"Username":"Agent00@gmail.com","PriorityNumber":0}, ' +
'{"Username":"Agent01@gmail.com","PriorityNumber":0},{"Username":"Agent02@gmail.com","PriorityNumber":0},' +
'{"Username":"Agent03@gmail.com","PriorityNumber":0},{"Username":"Agent04@gmail.com","PriorityNumber":0},' +
'{"Username":"Agent05@gmail.com","PriorityNumber":0},{"Username":"Agent06@gmail.com","PriorityNumber":0},' +
'{"Username":"Agent07@gmail.com","PriorityNumber":0},{"Username":"Agent08@gmail.com","PriorityNumber":0},' +
'{"Username":"Agent09@gmail.com","PriorityNumber":0},{"Username":"Agent10@gmail.com","PriorityNumber":0},' +
'{"Username":"Agent11@gmail.com","PriorityNumber":0},{"Username":"Agent00@gmail.com","PriorityNumber":1},' +
'{"Username":"Agent01@gmail.com","PriorityNumber":1},{"Username":"Agent02@gmail.com","PriorityNumber":1},' +
'{"Username":"Agent03@gmail.com","PriorityNumber":1},{"Username":"Agent04@gmail.com","PriorityNumber":1},' +
'{"Username":"Agent05@gmail.com","PriorityNumber":1},{"Username":"Agent06@gmail.com","PriorityNumber":1},' +
'{"Username":"Agent07@gmail.com","PriorityNumber":1},{"Username":"Agent08@gmail.com","PriorityNumber":1},' +
'{"Username":"Agent09@gmail.com","PriorityNumber":1},{"Username":"Agent10@gmail.com","PriorityNumber":1},' +
'{"Username":"Agent11@gmail.com","PriorityNumber":1},{"Username":"Agent00@gmail.com","PriorityNumber":2},' +
'{"Username":"Agent01@gmail.com","PriorityNumber":2},{"Username":"Agent02@gmail.com","PriorityNumber":2},' +
'{"Username":"Agent03@gmail.com","PriorityNumber":2},{"Username":"Agent04@gmail.com","PriorityNumber":2},' +
'{"Username":"Agent05@gmail.com","PriorityNumber":2},{"Username":"Agent06@gmail.com","PriorityNumber":2},' +
'{"Username":"Agent07@gmail.com","PriorityNumber":2},{"Username":"Agent08@gmail.com","PriorityNumber":2},' +
'{"Username":"Agent09@gmail.com","PriorityNumber":2},{"Username":"Agent10@gmail.com","PriorityNumber":2},' +
'{"Username":"Agent11@gmail.com","PriorityNumber":2}]}';

    //wrapper class
    public class JSON2Apex
    {
        public String DateModifiedUtc;
        public List<AgentInfoList> AgentInfoList;
    }
    public class AgentInfoList
   {
        public String Username;
        public Integer PriorityNumber;
    }
    public static JSON2Apex parse(String json)
    {
        return (JSON2Apex) System.JSON.deserialize(json, JSON2Apex.class);
    }
    public WSController() {
        info = JSON2Apex.parse(jsonStr);
    }
}

Date Modified: {!info.DateModifiedUtc}
<br />
<apex:repeat value="{!info.AgentInfoList}" var="AgentInfo">
    {!AgentInfo.Username} has priority {!AgentInfo.priorityNumber}.<br />
</apex:repeat>