Bull was born in 1985, in Sunbury, Victoria. He attended Sunbury Heights Primary, and graduated from Sunbury College in 2002, having been school captain. He went on to study at Deakin University from 2004 to 2007, undertaking a double degree in education and science.^{[citation needed]}

After completing his degree, Bull became a teacher. ^{[citation needed]}

Bull began his political career as an electorate officer for the former MP for Yuroke, Liz Beattie. He has also been chief of staff to the federal member for McEwen, Rob Mitchell. Bull has been actively involved with the ALP since 2003, serving as the Craigieburn Branch secretary for six years, a state conference delegate for three years, and a member of the Education and Youth Affairs Policy Committee and the Sport, Culture and Tourism Policy Committee.^{[citation needed]}

In 2013, Bull was accepted into the Australian Defence Force as an Army Reserve officer cadet, though he has been on leave due to work commitments. He is a keen runner with Melbourne running club "The Crosbie Crew", and completed his first marathon in 2014.^{[citation needed]}