Searching user from userstore

//execute query to find the user node
var luceneQuery = "@usr\\:username:\"johndoe\"";
var userStoreReference = "user://alfrescoUserStore";
var usersResultList = 
search.luceneSearch(userStoreReference, luceneQuery);
//get the user node and change enable property
var userInTheUserStore = usersResultList[0];
userInTheUserStore.properties["usr:enabled"] = false;
userInTheUserStore.save();