Conditionally aggregating documents in an index?

Elastic Stack Elasticsearch
1

I'm trying to conditionally aggregate documents in my index based on the existence of another document in the same set. Imagine the following series:

{"action": "pressed_submit", "user": 1, "timestamp": "2016-01-01 00:00:00", "meta": ...}
{"action": "answered_question", "user": 1, "timestamp": "2016-01-01 00:00:00", "meta": ...}
{"action": "answered_question", "user": 1, "timestamp": "2016-01-01 00:00:00", "meta": ...}
{"action": "filled_textbox", "user": 1, "timestamp": "2016-01-01 00:00:00", "meta": ...}
{"action": "pressed_submit", "user": 1, "timestamp": "2012-01-01 00:00:00", "meta": ...}

And then the following:

{"action": "answered_question", "user": 2, "timestamp": "2016-01-01 00:00:00", "meta": ...}
{"action": "answered_question", "user": 2, "timestamp": "2016-01-01 00:00:00", "meta": ...}
{"action": "filled_textbox", "user": 2, "timestamp": "2016-01-01 00:00:00", "meta": ...}
{"action": "pressed_submit", "user": 1, "timestamp": "2012-01-01 00:00:00", "meta": ...}

How can I find the last event done by each user that has not "pressed_submit"? Meaning, how can I find the last action by any user that hasn't pressed_submit? Note the timestamps.

I've been cracking my head around this for a while. While I've managed to solve the problem by querying ALL events and then filtering in Python code, it's very slow. Is there any way to use ElasticSearch's query engine to get results like that?