Laundrie, 23, disappeared after he initially refused to cooperate with police.
Petito was on a cross-country road trip with Laundrie, her fiancé, and was last known to have been in Grand Teton National Park late last month, when she stopped communicating with her family.
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They ran up and down the sidewalk, he proceeded to hit her, hopped in the car, and then drove off.
The report indicated that officers on scene had viewed Petito as the aggressor.
The where Laundrie and Petito were living with his parents on Monday.