What action types are possible for webhook asset besides CREATED?

I’m having trouble finding a comprehensive definition of the webhook JSON response for an asset. The examples I’ve found show a possible string of “CREATED”. But does anyone know what all possible string values are?

This is an example payload from the docs, but the description of this does not elaborate what values can be returned for the “action” field. I’m hoping to be able to track downloads of an asset along with the user who initiated the download and have that information be sent in a webhook. Thank you.

   "timestamp" : "2016-11-10T23:57:49.664+0000",
   "nodeId" : "52905B51-085CCABB-CEBBEAAD-16795588-FC927D93",
   "initiator" : "admin/",
   "repositoryName" : "npm-proxy",
   "action" : "CREATED",
   "asset" : {
   "id" : "31c950c8eeeab78336308177ae9c441c",
   "assetId" : "bnBtLXByb3h5OjMxYzk1MGM4ZWVlYWI3ODMzNjMwODE3N2FlOWM0NDFj",
   "format" : "npm",
   "name" : "concrete"