Scantron was the only way to take standardized tests when I was a kid. Armed with a number two pencil and a head full of potential, students would hunker down over these sheets and attempt to “fill in the bubble completely”, as per our teacher’s instructions. If you’re living with OCD, making sure that these little circles are completely and evenly darkened is akin to absolute madness. Trust me.

Sadly, the inventor of this testing format, Michael Sokolski, died on June 13 from congestive heart failure. He was 85 years-old.

Sokolski was born in Poland on September 25th, 1926. He lost his mother during a German attack on his homeland during World War II, an event which prompted him to serve in the Polish Forces under the British Eighth Army Command. Between the years 1945 and 1947, Sokolski served in Italy, fighting in the battle of Monte Cassino as a tank driver. During this exchange, Sokolski was wounded, earning him the Italy Star and War Medal for his service.

Following his graduation from the University of Minnesota with a Bachelor of Mechanical Engineering, the decorated war hero soon found work at IBM Rochester. In 1966, Sokolski founded Datronics, which he eventually sold to the 3M Corporation. Although he’d already made considerable progress in his career, the world wouldn’t know the man’s name until he formed Scan-Tron, which completely reinvented the way everyone took tests.

If all of this wasn’t enough to keep him busy, this tireless individual was a Technical Reserve for the Santa Ana Police Department in 1979, as well as a member of Advisory Board for the Orange County Sheriff Department. Following his retirement, Sokolski developed a passion for fishing, catching several 50-pound salmon during his many trips to the sea with his wife and family.

Although they may not know him by name, Twitter users are certainly aware of Scantron’s contributions to education. Below you can sample some of their reactions to Sokolski’s death.