who will add deliverable to activity

hello everyone

i have created one activity say (submit design doc) and added user1 as owner and user2 as resource, now i am adding a deliverable to this activity and i want user2 to add deliverable , but when i add user2 as owner in deliverable , then automatically activity owner is changed to user2, how can i manage that activity owner is user1 and deliverable added by user2

kindly provide the solution

thanks and regards

Nimish