Here is an API snippet you can use to find the user info associated with the change of an attribute's value. Note that not all changes/updates generate events, so this may not work universally, but for standard, built-in fields this should be useful.
for event in session.query('Event where parent_id is "<entity id>"'):
print('Event data: {0} triggered by {1}'.format(event['data'], event['user']['username']))