He died of liver failure, at the Hemet Valley Memorial Hospital. He was 49.
Although the rhythmic heart and soul of one of the heaviest bands in modern music, Hanneman was known as a soft-spoken, easygoing dude.
See also: Our Jeff Hanneman obituary
To pay tribute, we've reached out to players and peers he performed and spent time with for nearly three decades.
Below, members of Anthrax, Megadeth, Testament and others -- including Slash -- reflect on Hanneman and his contributions, and how he will be remembered.
"For me, Jeff Hanneman was the king of thrash/speed metal guitar. Slayer was the first speed metal band I ever listened to; the riffs & chord changes were genius. And that right hand blew my mind. Never heard anything quite like it."
David Ellefson, Megadeth
"Jeff was a low key public figure, but behind the scenes he was the engine that drove the machine of Slayer's music. His riffs, lyrics and fascinations with dark topics were so extreme that they were taboo even within metal music! But, because he dared to go there, he and the band became legend to fans everywhere. Behind all the bravado of Slayer's image and music, I knew Jeff as a kind and jovial man who always shared a laugh whenever we saw each other on tour together. He always struck me as someone who had his act together off the stage and as a result we would talk our personal and family lives away from music. He was a man of few words but when he spoke his words had impact."
Scott Ian, Anthrax
"There was a real dichotomy knowing Jeff. On one hand he was a really great guy, easy-going, very kick-back and chill, friendly, loved to laugh, and on the other hand he wrote some of the darkest, most brutal lyrics and riffs in the history of metal. If he had only ever written 'Angel Of Death' that alone would be enough to claim the throne of evil, let alone the catalogue of work he created. He was a singular talent and a fun person to be around. I'll miss him."
Charles Benante, Anthrax
"Jeff had a great fucking laugh, I heard it quite a bit throughout the years. The man who wrote such lyrics as "feel the knife pierce you intensely" had a great sense of humor. I will remember him for the music he gave and the intensity he brought to our metal world."
See also: The 20 Greatest Metal Albums in History
Alex Skolnick, Testament
"Like millions of others, I was deeply saddened to hear of the passing of Jeff Hanneman. Personally, I did not know Jeff well, despite our bands having done several tours together. He was someone with his own inside humor and he seemed to view life through the lenses of a wild party in which only those closest to him were invited.
But those he did let in clearly loved him a lot and will miss him dearly. Kerry King may have had the imagery, becoming the "face of Slayer". Tom Araya may have had the voice, so much so that Slayer is one of the few bands that has no background vocals during live shows. Drummer Dave Lombardo provided the musical virtuosity -- his playing forced drummers around the world to lock themselves away and rethink their technique. All four band members created the sound.
But it was Jeff Hanneman who brought in many of the band's most essential riffs. Ask any metal fan to list his or her personal favorite Slayer songs and it's a pretty safe bet that they'll mention one or more of the following sonic assaults, each composed by Hanneman: "Angel of Death," "Raining Blood," "South of Heaven," "War Ensemble," "Dead Skin Mask," "Seasons In The Abyss" and "Die By the Sword." For creating them, we all owe a big debt of gratitude to Jeff Hanneman."
"Slayer, or 'GoddamnfuckinSlayer' as they are affectionately known at KNAC.COM, starts with guitar. Jeff Hanneman's brutal guitar assault defined Slayer. He was the heaviest of the heavy. He even died in a way that should scare the shit out of you. Just like Slayer's music does. A tragic loss."
DJ Will, KNAC.com
"As I was resting up before heading down to the Golden Gods Awards I received a phone call from Doug Goodman, Slayer's very first tour manager, who told me that Jeff had died. I later played Show No Mercy in its entirely. One of my top five favorite metal bands of all time and one that I was fortunate enough to work with in the early days right out of high school.
The Hanneman/King guitar duo was never technical, but the distinctive trade off riffs/leads are 100% unmistakably Slayer! Sadly I had a feeling that the 2011 "Big 4" concert in Indio would be the last time all four original members would share the stage together, even if for two songs, as there seemed to be no real timetable for Jeff's return (despite Gary Holt from Exodus doing a masterful job in his own right). Slayer will always be an integral part of the Los Angeles music scene, because they made it without compromising or conforming, all the while influencing hundreds of other bands around the world over the years. I will miss my friend 'The Neck,' and my condolences go to the Hanneman family especially to 'Altar Girl' Kathy."
Steffan Chirazi, author
"Jeff was actually fairly shy. He loved playing, he loved writing, he loved to have fun but he was not in it for the attention whatsoever. We did many interviews over the years, and I always found his take on war, and war-related subjects, fascinating because it came from having been a child whose father and brothers had been in wars. It didn't come from movies, it came from life. Jeff was the thing which made the difference between Slayer being a good, strong metal band and a furious, cacophonous, addictive discordant flurry of riff-charged energy. His manipulation of hardcore punk, the way in which he fed its raw, feral anger into the writing, was absolutely what made Slayer both great and unique."