Writing Competition 130: "The time machine"

"Time is a fickle thing that can easily be broken. And when it eventually is, there is no saying what might happen."
The students soon started grumbling, telling the professor his time was up and that they had a match to attend. Without waiting for his approval even, they soon stormed out into the field.
The captain of the team wasn't at all friendly and soon he started bullying younger folks. His intention was to pass off the aggression he couldn't express at home.
To impress his girlfriend, he shot the ball off the premises during warmup and told one of the juniors around to go fetch the ball. It was usual to complain first, get beaten and then go for the ball anyway but this young chap 'Tunde' went without so much as uttering a word.
After a short pace, he found the ball and bent to pick it. But in the distance, he saw a 3D object and decided to check it out. When he got close, he soon found that the rig was open and someone had just left. By the right was imputed the day's date and time. Putting the pieces together, he concluded it was a time machine and stepped back. Remembering what the physics teacher had told them about time.
He picked up the ball that dropped as a result of the shock and went back to the field only to find the captain of the team Mofe with some other bullies running towards him angrily and yelling. He soon discovered that his life was at stake and resolved to use the machine as payback.
He ran into the rig, closed it and typed in the same date but 10 years back.
The captain and his mates got to the site marvelled and soon the rig disappeared. Tunde soon found himself displaced and back in time. He got out and tried locating the house of the captain who at the time was still a kid. He beat him up and told him never to lay hands on other kids else he would come back. He went back into the machine and imputed the date he left but hours after so the captain and his mates would've left the site. To his greatest surprise, the captain was there waiting, more ripped and rabid. It happened that Tunde only made things worst. As he tried to understand what had happened and how he was at the place he expected him not to be, these last words slipped out his mouth; "What have I done?"