During his weekly radio show on Thursday night, Purdue first-year coach Ryan Walters did not hold back.

Two days before his Boilermakers travel to Michigan Stadium to meet No. 2 Michigan, he spoke as publicly candid as any administrator or coach about the Wolverines’ alleged sign-stealing scheme.

“It's unfortunate. What's crazy is they weren't allegations,” he said. “It happened. There's video evidence. There's ticket purchases and sales that you can track back. We know for a fact that they were at a number of our games, so we've had to teach our guys a new language in terms of some signals.”

Purdue has the receipts.

In its own investigation into the matter, the university has found that Connor Stalions, Michigan’s now-suspended analyst at the center of the scheme, purchased tickets to six games at Ross-Ade Stadium over the last two years, sources tell Yahoo Sports.

They include four of the first five home games this year: Fresno State, Syracuse, Illinois and Ohio State. He bought tickets, as well, for home games in 2022 against Penn State and Northwestern.

Some of the tickets were transferred to accounts registered in names believed to be Stalions’ family members. The university has video footage from stadium surveillance of people sitting in seats that he purchased filming the sidelines. The university has presumably transferred such evidence to NCAA investigators.

Walters’ public comments echoed many private complaints from both Big Ten coaches and athletic directors in meetings with commissioner Tony Petitti over the last week. On Thursday night, as Walters was making his comments, the league’s athletic directors continued to urge action from the conference on what appears to be an elaborate, multi-year scheme to scout future opponents’ games to learn their play-call signals.

The scheme was elaborate enough that many Big Ten coaches knew enough of Michigan’s sign-stealing to alert TCU ahead of its win over the Wolverines in the CFP semifinal last years. In an interesting wrinkle, Ohio State made a request of clarification on the NCAA’s sign-stealing policy ahead of the CFP semifinals last year.

Sign-stealing is not against NCAA rules, but in-person scouting of future opponents as well as recording signals is. The NCAA is three weeks into its investigation into a scheme that has seen Stalions purchase tickets to at least 40 college football games, both within the Big Ten and those in contention for the College Football Playoff, such as Tennessee, Georgia, Clemson and Alabama.

However, Big Ten stakeholders are encouraging Petitti to take action now.

Walters is the first to take his feelings public, airing them on local radio before the Boilermakers (2-6) meet Michigan (8-0) at the Big House.

“We will operate differently offensively. You might see us in a huddle for the first time this season,” Walters continued on the radio show. “It is what it is. We're excited to go play.”

As more evidence emerges of the Michigan scheme, school administrators and coaches are becoming more vocal that Petitti should levy punishment and not wait for the NCAA’s probe to be completed.

In normal protocol, leagues rely on the NCAA for enforcement action. While NCAA probes can last months if not years, the organization’s foray into the Wolverines is on a more “accelerated” path, Petitti has told school leaders.

As early as last Thursday, athletic directors met with Petitti about the situation. A group of Big Ten presidents also met with Petitti last week over the issue after a scheduled meeting of the Big Ten Council of Presidents and Chancellors. Michigan president Santa Ono was originally on the call but then logged off so the others could discuss the situation.

Petitti is expected to meet with Ono on Friday while in Ann Arbor to attend the Big Ten field hockey tournament semifinals, according to The Athletic.

A decision from the league is uncertain, though options have been discussed. On their calls over the last week in fact, high-level school administrators and Petitti have pored over a wide range of possibilities. There was talk, for instance, of any penalty not impacting players directly. A suspension of head coach Jim Harbaugh may be the most likely and “cleanest” penalty if one were handed down, one source said.

Such a penalty from a conference is somewhat unprecedented and, if too severe, could eventually trigger legal action from the program, legal experts tell Yahoo Sports.

Any Big Ten penalty is rooted in the conference’s sportsmanship policy, which allows for the commissioner to hand down disciplinary measures for violating the “integrity of competition” in the “competitive arena,” the policy says.

The policy was at the center of discussions last week between school leaders and Petitti. According to the policy, the commissioner can take disciplinary action that is considered “standard” or “major.” Standard action includes a fine not exceeding $10,000 and a suspension of no more than two contests. Major action is anything exceeding those penalties and is subject to approval from the Big Ten executive board of presidents.