Well, that could have gone better, Matt thought, standing over the dead body of his best friend's father, who was also the Overseer. His mind couldn't come up with another solution at the time; his own father, James, one of the brightest minds of the Vault, just left him there, all alone, with the entire facility searching for him now. At first, he thought they might have just wanted to know where his father had gone (to which he had no answer, as he hadn't told him of his departure), but when he learned they had murdered his lab partner, Jonas, a man who had been like an uncle to Matt, he knew they probably didn't just want to "chat."
Throwing away his thoughts for a moment, he grabbed the password to the Overseer's terminal, a code that would allow him to escape to the outside world to search for his missing father. Proceeding to the vault door, he ran into Amata, his best friend, who had witnessed the murder of her father. She was sobbing as Matt tried to comfort her.
"Amata, please… I didn't mean to… he just… he was trying to kill me… you must understand, I-"
"Save it," she cut in sharply. "I don't want to talk to, or hear from you, ever again…" She continued sobbing, walking towards her father's body.
"Amata, listen to me, please…" He thought for a moment, when she turned around to look him, with tears streaming down her face, that she might give him a chance. How wrong he was.
"Just get out of here, before I call the other guards to come and arrest you," she said coldly, and continued walking. Matt hung his head low, and turned to the office, where he found the Overseer's terminal, on and ready to go.
Punching in the code quickly (which was simply 'Amata') he chose to open the Vault door, something which hadn't been done since… ever. With the sirens sounding, lights flashing, and guards closing in, he stepped out into the cool breeze of the underground tunnel, and the Vault door shut behind him.
Armed with his baseball bat and a pistol, he walked down the old pathway, thinking all the while why his father may have left him. Did I do something wrong? Does he know someone from the outside? Did he just want a bit of fresh air? All of these questions came to mind as he thought of his father; a strong-willed, amusing man, not only wise about science, but also wise with his words. Everything Matt knew came from his vast knowledge, and without his presence in his life… well, Matt just didn't know what to do.
He kept walking and came across some radroaches. He whipped out his baseball bat and beat them to a pulp. God dammit, why does it always have to be radroaches?! Angry with himself and the vault dwellers, he continued to beat down on the roaches for several minutes after they were dead. He found himself crying a little, and he put away the bat to wipe the tears from his eyes.
As he approached the final gateway to the outside world, he vowed that no matter how long it took, he would find his father, or at least, what happened to him, and that when he did, he would smack him senseless.