Police have arrested and are soon expected to charge the second suspect who helped former University of Minnesota quarterback Philip Nelson brutally assault Isaac Kolstad.

According to the Minneapolis Star-Tribune, authorities are expected to charge Trevor Shelley, 21, with assault Wednesday. Authorities and eyewitnesses both say it was Shelley that threw the punch that knocked Kolstad unconscious.

The Associated Press reported Shelley has been charged with two counts of felony assault.

Kolstad, a 24-year-old graduating senior and linebacker for Minnesota State University, is in critical condition at the Mayo Clinic facility in Mankato. Isaac's father Blaine posted an update to his website CaringBridge.org stating his son underwent a successful surgery but is still in critical condition.

Kolstad suffered a fractured skull and a swollen brain, as well as lung damage, but it is unclear if he will have long-term problems. Authorities said the attack late Sunday night lasted five to 10 seconds and ended with Nelson kicking Kolstad's head "like a soccer ball."

Nelson was arrested early Monday morning then later charged with first- and third-degree assault charges. He was then released on $20,000 bail. Authorities say the altercation resulted from Nelson confusing Kolstad for a bouncer who kissed his girlfriend's had at a local bar.

Police posted surveillance video of a mysterious person in a red shirt fleeing the scene Monday evening and Shelley was identified and arrested in his home about four hours later.

Todd Miller, Mankato's public safety director, told NJ.com Kolstad and Nelson played football in the town's rivaling East and West high schools.

Kolstad is married and has a daughter, but his wife is pregnant with their second child.

Nelson was Minnesota's starter for two years, but was going to transfer to Rutgers, however the school announced he would be dismissed from the team. Nelson faces a maximum sentence of 25 years in prison if convicted, which would increase if Kolstad does not survive.

"Isaac suffered a severe head injury early this morning," Blaine Kolstad wrote shortly after Isaac was brought to the hospital. "He is currently in Critical condition and fighting for his life. He is young and strong, but the battle he has in front of him is enormous. We do not yet know the full extent of his injuries. He is very sick. Please pray for Isaac and all of those involved."

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