Anonymously Attacked

Today, I was walking under a covered bridge when I got attacked. Who was/were my silent assassins? I will probably never know. I was walking under a covered bridge at the college. I heard a loud thud on the metal roof and saw a pine cone bounce off. Wow, that was loud. Seconds later, boom. Only this time, it was much louder. My attackers were no longer using pine cones. Then another one. I quickly walked to another area. I like to think it was a tribe of angry squirrel council men attacking me, but I will never know. Next time, I'll be ready for them though.