The Sumerians considered life after death as a bad place to be in.
It was ‘The house where they sit in darkness, where dust is their food and clay their meat, they are clothed like birds with wings for garments, over bolt and door lie dust and silence.’
This was their hell, Sheol as it is called in the Bible and many other ancient texts.
Regardless of the notion of life after death as a bad place to be, there is evidence of rituals involving virtual suicide. Attendants of kings and queens were buried buried along with their masters. (Sounds very much like Egypt.) This also shows that Sumerian believed in life after death. The attendants and other accessories were buried with the kings (and queens) to make sure they remain comfortable in the life after death.