Automatic merge triggering duplicate Jenkins

[Barak Ben-David]

My setup is as follows:

1. I have implemented branching model: development (default), release and production (master)
2. I enabled automatic merge
3. Merge strategies - --ff-only
4. Jenkins Jobs: 
   1. filter on development branch
   2. filter on release/* branch(s)
5. Using Bitbucket hook for Jenkins plugin (free version)

Actions taken:

1. PR into development branch - job 1 triggers no problem
2. PR development into release/* - Job 2 triggers AND job 1 triggers TWICE:
   1. when PR is created
   2. when PR is merged (automatic merge tries to merge back into development, even though the commit hash has not changed and no new merge commit is created with --ff-only strategy enabled)

Expected:

Job 1 (filter on development branch) should trigger when creating a PR from development into release/* since no new commit hash is created (--ff-only).

Also, why is it triggering on PR created? I thought the plugin (free version) only send a request for PR Merged.