(CNN) -- Rutgers University Athletic Director Tim Pernetti has resigned in the wake of a player abuse scandal that prompted the school to fire its men's basketball coach earlier this week.
In a resignation letter to the school's president released Friday, Pernetti said that his "continued tenure as athletic director is no longer sustainable for the university."
Pernetti had come under fire for not initially taking more serious disciplinary action against coach Mike Rice, who was fired Friday after ESPN aired a video that showed him shoving and berating players.
In his letter, Pernetti wrote that his "first instincts" after seeing the video last year, months before ESPN aired it, "was to fire him (Rice) immediately."
"However, Rutgers decided to follow a process involving university lawyers, human resources professionals, and outside counsel," Pernetti wrote. "Following review of the independent investigative report, the consensus was that university policy would not justify dismissal.
"I have admitted my role in, and regret for, that decision, and wish that I had the opportunity to go back and override it for the sake of everyone involved."
The video initially had earned Rice a three-game suspension, a $75,000 fine and a ticket to anger management classes.
ESPN, which aired the video Tuesday, said it shows practice sessions shot between 2010 and 2012 in which the coach also threw basketballs at players.
"You f**king fairy ... you're a f**king fa**ot," Rice appears to say during one session.
An assistant coach resigned the same day the school fired Rice.
Before he resigned, Pernetti had said he made a mistake in favoring suspension for the head coach.
"I am responsible for the decision to attempt a rehabilitation of Coach Rice," Pernetti said in a written statement. "Dismissal and corrective action were debated in December and I thought it was in the best interest of everyone to rehabilitate, but I was wrong."
"There's no explanation for what's on those videos because there's no excuse for it," Rice said after he was fired, according to CNN affiliate WABC. Still, he will walk away with a $100,000 longevity bonus, according to the university.
CNN's Mark Norman and Jason Durand contributed to this report.