Police said Martin Duckworth boarded a Metro bus Aug. 12 in downtown Seattle, pulled a gun and shot and wounded driver DeLoy Dupuis.
They say Duckworth then tried to carjack a delivery truck and a car before boarding a second bus and raising his gun and pointing it at officers. Officers fired several rounds, fatally wounding him.
The Seattle Times reported court records showed Duckworth had a history of drug and mental health issues.
King County Prosecutor Dan Satterberg recommended the inquest after reviewing material from Seattle police. Executive Dow Constantine ordered it Friday.
Inquests are fact-finding hearings conducted before a six-member jury.