I'm looking to create a case comment and update some of the case fields in a trigger.  This is what I have so far, but I get an error saying the record is read-only ( These lines c.Status = 'Pending'; c.Priority = 'Low'; c.CW_Type__c = 'Task';)
 

trigger CW_DSS_CaseTrigger on Case (after update) {
  if(CWcheckRecursive.runOnce())
    {
    
   List<Case> cwCasesUpdated = new List<Case>();
   List<caseComment> caseCommentList = new List<caseComment>();
    for (Case c: Trigger.new)
    {
        
        caseComment cc = new caseComment();
        if(c.Macros__c == 'Application Support information'){
                cc.parentid = c.ID;
                cc.commentbody = 'For application (DSSi and Relay Server) support and troubleshooting requests, please provide the following information.'+'\n' +
                                    'Minimum DSS Ticket Information requirements:'+'\n' +
                                    'Site Name:' +'\n' +
                                    'Site Contact: (For possible Site IT related issues)' +'\n' +
                                    'DSSi Software Version:' +'\n' +
                                    'Problem/Inquiry:' +'\n' +
                                    'Troubleshooting Steps Taken:' +'\n' +
                                    'This information is required with all DSS support requests. Failure to provide this requested information may delay your request.';
                cc.ispublished = true;
                cwCasesUpdated.add(c); 
                casecommentlist.add(cc);
               
        }
        if(c.Macros__c == 'Blackbox - Out of Scope'){
                cc.parentid = c.ID;
                cc.commentbody = 'Blackbox data requests can only be processed for incidents that occur involving driver fatigue, personal or property damage' +'\n' +
                'and injury related to fatigue or distraction and operator tampering.  The DSS is not to be used for disciplinary actions for mine safety violations.'+'\n' +
                'This eliminates sites wanting blackbox video for mine safety infractions, evidence of medical related injuries or diagnostic reasons.' +'\n' +
                 'This is to only be used if necessary to add evidence, clarify or discovery information about an incident or accident involving fatigue and/or distraction.';
                cc.ispublished = true;
                c.Status = 'Pending';
                c.Priority = 'Low';
                c.CW_Type__c = 'Task';
                casecommentlist.add(cc);
               
        }
       
    }
            insert caseCommentList;
            
          
    }
}