Calling Another Process without moving main process

I am trying to call another process inside a process, but I want to keep main process steady.
I tried boundary message events, but I could not find a way to keep main process not to move forward.
What I want to model is that
Process 1
User Task 1
User Task 2
Process 2
User Task 3

I want to start user task 3 from user task 1 , and I do not want to process 1 to pass user task 2
Is there anyway to do this ?

use a Call Activity in the parent process to call the sub process.

This will close user task 1 . My business case requires keep user task 1 open and start other process asynchronous

You can trigger it from the user task with a non-interrupting event. like this: