Those are very sad news. RIP Ola Brunkert .You've given us so much.
Ola Brunkert's biography
Ola Brunkert had been a jazz drummer, also being a member of the blues band Slim's Blues Gang, before joining pop group Science Poption in the mid-1960s. Then, through working with guitarist Janne Schaffer in the jazz-pop group Opus III later in the decade, he started getting work as a session musician from 1970 onwards.
Ola's first known ABBA-related session was also the group's very first single, People Need Love. Together with bass player Rutger Gunnarsson, Ola is probably the only musician to appear on all ABBA albums - he was one of the most frequently used Swedish sessions musicians during the 1970s. Ola also toured with ABBA in 1977, 1979, and 1980.
http://www.abbasite.com/people/bio.php?id=409