Cyclone junior defensive end Cephus Johnson was arrested Saturday and charged with serious assault.

The arrest came after a weeklong investigation into claims that Johnson, junior in sociology, punched Nicholas Zeitler, junior in computer engineering, on Jan. 14 at Mickey’s Irish Pub, 109 Welch Ave.

Jacki McKeighan, an employee of Mickey’s, said she was working at Mickey’s on the night of the assault but didn’t see anything. McKeighan said that, as far as she knows, a fight between Johnson and Zeitler started in the bar, but then Johnson, his friends and Zeitler went outside.

McKeighan said Johnson showed her manager that he had a knife. McKeighan said her manager called the police, but they didn’t come into Mickey’s because Johnson was outside when police arrived. According to records, the police were called at 2:11 a.m. Police have not confirmed whether a weapon was involved.

Johnson had 23 tackles in 2004. He is the second ISU football player to be arrested for assault this academic school year. Former Cyclone football player Jason Berryman is serving a 300-day jail sentence for serious misdemeanor assault and felony first-degree theft for an incident on Aug. 4.

— The Associated Press contributed to this article.