From Halopedia, the Halo wiki
One night, he got drunk and decided to use his dad's gate pass to borrow a Warthog from the base motor pool to go joyriding. He managed to flip it upside down and couldn't return it. Desperate to keep his dad from getting it in trouble, he convinced Jan to sneak into the base to return the gate pass. Jan was successful but was apprehended by military police after leaving the base.
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