They released a statement on Facebook. 

The decision has been made with great regret that the 2015 MPAJF football season has been cancelled. After continued threats against League officials, coaches and referees, the League has only one option, to cancel the season. Today, October 13, 2015, ammunition shells were placed at the field gate with names of League officers printed with permanent marker. Due to the increase in violence of these threats, the safety of our children is the main concern. Decisions of this magnitude are not done lightly; rather they are done with the advice of the State Police, FBI, school administrators and League Officials. We hope that as parents you will agree with this decision and try and cooperate with everyone involved to bring forward the person or persons responsible for these actions. The league’s future and our children’s continued participation in future seasons is what is in jeopardy.

What is wrong with people!!! 

http://deadspin.com/youth-football-league-cancels-season-due-to-violent-...