4th arrest in attack on now-Denver Broncos draft pick, running back Montee Ball

MADISON, Wis. - The fourth and final person charged in an attack on Denver Broncos draft pick Montee Ball is in custody.

Karlis Griffin, 28, was arrested on a warrant in Chicago last week.

A criminal complaint says Griffin stomped on Ball's head during last summer's attack as Ball was walking home with three friends in Madison. Ball suffered a concussion and says he doesn't remember the attack.

Ball was a running back for the Wisconsin Badgers at the time of the attack. He was drafted in the second round by the Denver Broncos months later.

The State Journal says Griffin has a prior felony battery conviction in Wisconsin.