Because he can't let her go that easily
When he first hears that she's dead, he freezes. His brain refuses to compute Tony's words and he's in the desert again, surrounded by lonely sand and burning sun and it's always a phone call.
He never makes it in time to save the ones he loves.
"Boss? Are you there?" Tony asks, his voice clearly tangled in regret and sorrow and concern and Gibbs forces himself to move. He makes his gruff voice clear and audible and says
"Wait for me,"
He hangs up the phone. Brusque is his middle name after all. They shouldn't read anything more into it (but his team know him by now and of course they do).
It's a long way to the diner in the desert, and he travels it alone. It would make him laugh to think of how he always winds up in a car by himself but Gibbs is still functioning happily in numb mode where feelings don't need to register.
This is a case; there are no time for his pesky emotions and he's a private person anyway.
Still, the flight and consequential hours of driving like to wreak havoc on his self control no matter what his brain says. He forces his tense body to sleep on the plane, drifting lightly in and out of troubled rest for the entire time and never allowing the nightmares to sneak up on him. That's not an option in the car, but he's too fragile to play any of his music.
Music is hard at the best of times. Days like this are far from that.
He stops only for fuel, and fuel for himself is forgone because he can't.
His two agents wait patiently for him when he finally reaches the abandoned diner, and he's not disappointed in them for calling in all of the proper channels despite his lack of permission. Tony and Ziva are good at their job, and they have a backbone that withstands even his crushingly heavy gaze. He could never be disappointed in that.
Gibbs dislikes that Leon Vance is there first, is there at all, but the man is surprisingly gentle and considerate.
"She put up a good fight," he says, and Gibbs looks him square in the eyes, because of course Jenny did. That was who she was, and he loved her for it (and once upon a time she loved him back).
The blood is the only thing that remains on the floor. Jenny- the body- is already gone and he hates Leon for that, but at the same time he doesn't know if he could handle another addition to his nightmares. He's grateful, and he will still force the crime scene pictures from DiNozzo later on.
"You watch him," Gibbs tells Tony, and it hits him properly, for the first time, that she's gone. She's never coming back. This isn't Paris; she hasn't gone to live a happy life and become successful and decided that he is nothing more than a footnote in the story of her life; Jenny is dead.
He swallows roughly and strides away from his agents, around the back of the building, and allows his iron strength to falter for a moment. His calloused hand stretches out and impacts against the wall, steadying him as he folds in half with the new burden of her death added to his back. He clenches his teeth harshly, sucking in a half gasp of air reminisce of a sob that nobody who knew him could quite label it as, then screwed the lid back on the jar and stood back up.
It was not the time for anything other than action.
The sterile rooms of autopsy look colder than he's ever seen them, and so he ignores them in favour of the black body bag that lies in front of Ducky.
"Jethro-" Ducky begins, but the man knows Gibbs well enough to read the crease of his brows and not say a word.
He reaches down, intending to unzip the bag, but for some reason, his hands rest gently on the space where her face hides under the bag. His touch is soft, fleeting, and it's a clearer declaration of love than most that he gave to her when she lived. His fingers can't help but caress down the black material, remembering a smooth cheek and a lively set of eyes that never stopped looking around at the world around her.
Gibbs tears his hands away from the useless task and grabs a zip, pulling it open like he would any other bag. It's a little stuck, so he uses his other hand to complete the task, only to discover that the other zip doesn't work either.
He tries harder, his jaw clenching as he clamps down on any unruly emotions that want to escape him, and still the zips won't unzip.
He looks down at the bag one last time, then walks away without a word.
He'll try again later. Maybe the zips could be opened if there was more privacy.
Later takes a long time to come. It doesn't come until after he confronts Natasha and Leon, until after he sets Jenny's house and family home on fire, until after he's said his goodbye to Mike.
It's well past midnight when he has the time and courage to venture downstairs again. The autopsy room is unlocked, for once, and Gibbs is glad to have a friend that understands him as well as Ducky truly does.
There's only one bag out on the tables this time, and he knows he can't avoid it (or her) any longer. Still, it's one of the hardest things he's ever done to pull down the zip and reveal her face, peaceful in death like it rarely was in life, and he's struck by how young she looks without the tension that came with the job of Director.
She hasn't changed a bit since Paris.
Her hair is fanned around her (she hated having her hair down because it was so impractical) and it's long again, like when she first became Director. Jenny liked to change hairstyles a lot and he always ended up liking the newest one, no matter what it was, because it was always Jenny and no matter what she said or did, he always loved her.
He reaches out with one hand and it's trembling slightly, as he notes with slightly detached interest. He allows himself to stroke her cheek once, the way he would have done every day had she let him, and then takes his hand away before he can hurt her.
His knees feel a little weak, but he ignores it the same way he ignores the way he knows both his hands are trembling violently and focuses entirely on her.
"Jenny…" he whispers, the name a mere exhalation as he breathes steadily in and out, in and out, in and out, and then his breath hitches and he can't force it back to normal like he usually does. It judders with every breath he tries to take or release, and with it, his eyes begin to burn. He's used to that one; most evenings he ends up alone in his basement with only ghosts for company and the one thing that ghosts are good for is causing his eyes to water.
Looks like there was a new ghost to add to the collection.
He can't force the tears not to come, and so they pour over him in waves of sorrow, forcing him to his knees and then to the floor. They begin to run off of his face and onto the hard linoleum surface, so he buries his face in his arms instead, and leans against the table where Jenny lies dead. He pulls his body in, curling into the smallest space he can manage, and weeps openly into his arms.
He cries for her; because she is passionate and lively, witty and brave and determined. She is a best friend and a love, and she was once something more, and so he cries for the regrets that they can never fix and for the problems they caused each other that could have been so easily put back into place.
It takes him longer than he'd ever admit to pull himself together again. Gibbs almost doesn't want to, because if there's anybody that deserves his grief, it is Jenny, but he knows that life will go on. It will continue to move, a little less vibrant and with a little less meaning, but it has to continue and he has to go with it.
That's another truth that he learns from death. In future days, he sometimes hates her for being able to escape so easily when he is forced to remain behind and live on whilst everything he loves is gone.
For now, he loves her, and so he eventually manages to pick himself off of the floor, wincing slightly as his bones creak and protest his impromptu fit of grief. He wipes away any remnants of tears that linger on his face, and looks down one last time on Jenny.
"Goodbye, Jenny. Good luck," he says simply, tenderly tucking away a strand of brown hair from where it fell over her ear. He hesitates for a moment, then leans in and kisses her lips, one last time, one last memento.
He stands up and walks away.