[1][2] Klein was born into an evangelical family in Vienna where he received training in building and stone carving trades and completed two years of architecture studies at the Academy of Fine Arts Vienna.
He moved to Croatia in 1851, successfully applied for a job as a bricklayer foreman in the Varaždin-Đurđevac Regiment, and spent the next eight years working for the Regiment in Bjelovar, until he was transferred to Zagreb in 1859.
[3] It is known that Klein designed and built a number of public buildings during his stay in Bjelovar, but there are no surviving records that would support a reliable attribution.
[4] His earliest known work is the Church of the Assumption of the Blessed Virgin Mary in Molve, built between 1855 and 1862.
[6] He also built Zagreb Orthodox Cathedral located on the Petar Preradović Square.