Damn. Brent Hinds, founding lead guitarist of Mastodon, left the band this March for unknown reasons, and all parties were initially quiet about the reasons. More recently he started posting angry tweets about being kicked out of the band, and things got uglier. Yesterday he was killed in a motorcycle accident, when a woman turned left without signaling in front of him.
It sounds like he had a lot of stuff to work out, and like any band breakup, I always have hope they can sort their differences and work together again; I do hope the band can continue making excellent music. Several of their albums have been inspired by personal tragedy, but this just seems cruel.