Maybe the aggressive cows are getting their own back for the "cow tipping" urban myth... by trying "human tipping".

Cow tipping was a bizarre, dangerous and illegal phenomenon that reached a peak in popularity in the late 1990s. Cow tipping consisted of people, usually bored teens and preteens living near farming communities, pushing over sleeping cows. Since cows sleep standing up, the tipped cows would simply fall from their standard vertical position... to a horizontal one. The cow would either stay asleep on the ground or wake up as it landed with a thud. Supposedly, the cow tippers found entertainment in watching the stunned and unhappy cow's reaction