sätze korrigieren

hallo,
könnt ihr meine Sätze bitter verbessern?
danke
After researching on the internet I get to know that a black man was shot and then the riots started.
30% people of who belonged to a gang set an appointment at 1 o`clock and said the incident is just for fun. The situation which took some days got out of control. There even were murderer. The age of the people was from 11 to 40. There were too less policemen and too less police control. I hope something like this will never happen and that the social problems get less.