Well, ackchyually...

Casey Chaos only sang on a demo tape titled "Ghetto Blaster Rehearsals", recorded in 2003, with Daron Malakian on lead guitar. While this demo was credited to the name Scars On Broadway, the band was only formally announced following System Of A Down's hiatus in May 2006 as a project by Malakian (as the lead vocalist) and System Of A Down drummer John Dolmayan.

In a statement on the band's website in 2007, Scars On Broadway clarified that these demo tracks were not affiliated with the band as it exists today, as they were from a disbanded project that had ended four years earlier.

All this to say that crediting Casey Chaos as the vocalist for Scars On Broadway seems a bit too generous and somewhat misleading.

He had suffered a massive heart attack.

"Casey had been dealing with heart issues, poor circulation, and high blood pressure for the last few years

https://blabbermouth.net/news/casey-chaos-official-cause-of-death-revealed