Understanding an UPDATING_DELETED_ROW Conflict

User 2 query:

{
            "creates" : [],
            "updates" : [],
            "deletes" : [
                            {
                              "entityType" : "Employee",
                              "dbGeneInternalId": "john_smith_id",
                              "fieldValues": []
                            }
                        ]
}

User 1 query:

{
            "creates" : [],
            "updates" : [{
                                       "entityType" : "Employee",
                                       "dbGeneInternalId": "john_smith_id",
                                       "fieldValues" : [
                                           {
                                               "fieldName" : "age",
                                               "newValue" : "41",
                                               "localValue": "40"

                                           }
                                       ]
                                   }],
            "deletes" : []
}

User 1 query response:

{
            "created" : [],
            "updated" : 0,
            "deleted": 0,
            "conflicts": [
              {
                  "entityType" : "Employee",
                  "dbGeneInternalId": "john_smith_id",
                  "conflictType": "UPDATING_DELETED_ROW",
                  "fieldValues": [
                    {
                        "fieldName" : "age",
                        "newValue" : "45",
                        "localValue": "40"
                    }
                  ]
              }
            ]
}