A letter sent to former Astros general manager Jeff Luhnow from MLB commissioner Rob Manfred in January sheds even more light on the Houston sign-stealing scandal that rocked baseball.

In the previously undisclosed letter, the Wall Street Journal reports Luhnow was made aware of an Excel-based application “programmed with an algorithm that could decode opposing catchers’ signs,” dubbed “Codebreaker.”

The program worked by logging a catcher’s signs and ensuing pitches into a spreadsheet to determine what the signals meant. That information was relayed to baserunners, who in turn shared it with hitters. The Astros players became brazen, watching the live feed on a monitor near the dugout and announcing the incoming pitches to hitters by the now-infamous method of banging on a trash can.

Luhnow admitted to having been shown the program by an intern in 2016 — which another Astros employee referred to multiple times as “our dark arts, sign-stealing system” in emails to the ex-GM. Luhnow claimed he didn’t read those reports far enough down to see the tidbits referencing the cheating, and MLB was unable to show he encouraged its use or even knew how to use it.

That didn’t stop Manfred from pointing a finger squarely at him.

In his letter to Luhnow, Manfred wrote, “there is more than sufficient evidence to support a conclusion that you knew — and overwhelming evidence that you should have known — that the Astros maintained a sign-stealing program that violated MLB’s rules.”

Not long after that, Luhnow and manager A.J. Hinch were suspended for a year by the league, and hours later both were fired by the Astros.