The passive voice removes the subject from the sentence. It is formed with the verb to be and the past participle of the main verb.
The bill was resubmitted by the Senator.
Unless you want to de-emphasize the doer of an action, you should favor the active voice. Passive sentences are usually considered loose.
The Senator has resubmitted the bill.
The head of the insurgency was reported killed in the first day of action by the press.
The passive structure seems to imply that the press killed the head of the insurgency. In the construction killed in the first day of action by the press drop the intervening phrase in the first day and you get killed by the press. The sentence is better expressed at least partially in the active voice:
The press reported that the head of the insurgency was killed in the first day of action.
Here, the subject press uses the active verb reported, and presumably the army is alluded to by the passive verb was killed.