As response units arrived, several staff members were able to escape through a back door, with some taking shelter at a dental practice next door.
Other hostages were later allowed to leave — all with the exception of Dr Dodson.
Escapees told police the assailant had a pistol, a shotgun and two duffel bags.
As police negotiators pleaded with Narumanchi to stand down, other officers scrambled to learn what they could about him.
It emerged that the 43-year-old had been recently diagnosed with terminal cancer, and had been told he only had weeks to live.
Investigators also quickly learned that Narumanchi had applied for a volunteer position at the children's medical center just one week earlier — but had been turned down, for a reason that has not yet become clear. It is his only known connection to the workplace.