Looking for a Zombie Movie Title.

I remember watching a movie on Xfinity On Demand roughly 10 years ago. It was a thriller, a film about a group of young adults (possible college students) who went to a rave party/concert on an island. During the concert, a zombie apocalypse broke out and the group of people were attacked, a few students survived. It was set at night on a dark and forest covered island. I remember a specific scene of someone trying to get in a window, but their lower half of their body was eaten and they died as other survivors pulled them through. The survivors covered the body, only for it to turn into a zombie and attempt to attack them.

I saw this movie so long ago so it’s difficult for me to remember. My sister and I are trying our best to find it, but no luck. Can anyone else help?