The principal of a Des Moines-area high school sent parents a message Sunday night about security following three fights that broke out between students at West Des Moines Valley High School Thursday.

Messages described as “racially-charged” were posted on social media sites earlier that evidently provoked at least one of the brawls and video of at least two of the fights was posted on YouTube.

A threat was issued anonymously Thursday night promising shootings the next day and on Friday, about a quarter of the school’s students were absent. Valley Principal Tim Miller is promising parents there will be a much greater police presence at the school until they feel the environment is back to normal.