Database
[{"_id":ObjectId("5deb4ce4bbe1b67e6e5611e4"),"site":"MDC","label":"407","status":"removed"},{"_id":ObjectId("5def36379ca17632de773d7e"),"site":"MDC","label":"407","status":"new"},{"_id":ObjectId("5df4740eab0d76657c19a7d2"),"site":"MDC","label":"408","status":"new"}]
Query
db.collection.aggregate([{$group:{_id:"$label",old_id:{$first:"$_id"},site:{$first:"$site"},status:{$push:{label:"$status"}}}},{$project:{_id:"$old_id",site:1,label:"$_id",status:1}}])