A Darwin doctor examined an "agitated" man wandering in and out of a hospital asking for a poison antidote and found no signs of mental illness, a court has heard.
Hours later, the same man, Benjamin Glenn Hoffmann, allegedly gunned down four people in less than an hour.
Hoffmann has pleaded not guilty to four counts of murder at four locations during an afternoon shooting spree on June 4, 2019.
In the hours before, the 47-year-old drove to Royal Darwin Hospital where he told an emergency department doctor he feared he'd been poisoned.
"He was hanging out with some fairly disreputable people," Ross Dryden said, referring to his notes written at 7.10am after his consultation with Hoffmann.
"He suspects they poisoned his energy drink."
Dr Dryden said he performed an examination and an electrocardiogram, and the results came back normal.
It was the second time Hoffmann had gone to the hospital asking staff for an antidote that night.
Receptionist Jessica Porter said Hoffmann tried to give his phone to her and repeatedly walked in and out the doors to the empty waiting room.
"He did seem agitated and worried," she said from the witness box in the Northern Territory Supreme Court on Tuesday.
Another receptionist Hayley Bunker said Hoffmann was "paranoid and scattered" and he looked "wide-eyed".
"He was speaking very quickly she was saying strange things," she said.
Nurse Rohan Williams said Hoffmann's nervousness caught his eye.
He said Hoffmann asked for a blood test to find out what he'd been "spiked" with.
"He was sitting bolt upright in the chair," he said.
Mr Williams told Dr Dryden he thought Hoffmann was likely under the influence of methamphetamine.
Hoffmann later told Dr Dryden he felt disorientated, vague and not balanced
Despite this and Hoffmann's "abnormal" behaviour, Dr Dryden developed no concerns about his patient's psychological state.
"It wasn't a mental health presentation," he said.
"I see lots of unusual people in the course of a shift. I don't refer them all to mental health."
Dr Dryden advised Hoffmann to go home and "see how he goes" and come back if was still unwell in the evening.
Hoffmann did return to the hospital but it was under a police guard after he'd allegedly shot four people dead 11 hours later.
The Crown says his first victim, Hassan Baydoun, 33, died about 5.38pm at the Palms Motel.
Hoffman then allegedly shot Nigel Hellings, 75, at an apartment block and Michael Sisois, 57, in a car park.
Rob Courtney, 52, was stabbed more than 30 times and shot dead at Darwin Recycling.
Earlier, the court heard Hoffmann pulled his car into a service station about 6pm on June 3 and gave his mobile phone to cashier Edith Reidy.
"He was scared," she said.
CCTV footage shows Hoffmann coming and going from a Puma service station on Darwin's outskirts.
In the video, Ms Reidy can be heard telling another customer about Hoffmann after he handed his phone to her.
"A fella just ran in here and said if anything happens, ring the cops," she told a bearded man dressed in a brown shirt.
"F*** this s***. Why did this happen to me?"
The bearded man advised Ms Reidy to call the police and tell them about Hoffmann.
In a statement to police, Ms Reidy said Hoffmann told her he was in trouble and they were after him.
She was unable to say who "they" were.
"I could see his face looking at me terrified," she told police after the killings.
About the same time, Hoffmann smoked crystal methamphetamine with his ex-girlfriend, Kelly Collins, at her home in a nearby suburb.
Hoffmann told police after he was arrested that he believed he'd been poisoned the night before the killings.
He said it caused him to be "out of his mind" and temporarily insane.
The trial continues.