How to search only People using javascript (sp.search.js)?

My code:

$("#searchButton").click(function () {        
var keywordQuery = new Microsoft.SharePoint.Client.Search.Query.KeywordQuery(context);        
keywordQuery.set_queryText($("#searchTextBox").val());        
var searchExecutor = new Microsoft.SharePoint.Client.Search.Query.SearchExecutor(context);	
results = searchExecutor.executeQuery(keywordQuery);        
context.executeQueryAsync(onQuerySuccess, onQueryError);    
});        
function onQuerySuccess() {        
$("#resultsDiv").append('<table>');        
$.each(results.m_value.ResultTables[0].ResultRows, function () {	    
$("#resultsDiv").append('<tr>');            
$("#resultsDiv").append('<td>' + this.Author + '</td>');            
$("#resultsDiv").append('<td>' + this.Title + '</td>');            
$("#resultsDiv").append('</tr>');        
});        
$("#resultsDiv").append('</table>');    
}

But this code actually find all results. How to filter to show only People results?