Uploading Komento attachments to Amazon S3

I have a site built in AWS Elastic Beanstalk so it's a scaling environment and local resources won't work. What trigger ( http://stackideas.com/docs/komento/administrators/advance/triggers ) can I build a plugin around so that I can access uploaded attachments details? I've tried onBeforeSaveComment, but I'm not seeing anything about attachments in the object. I really need to get these into S3