"I saw him clutching his head and he was closing his eyes tightly and his face was very red and he was sweating profusely," Nik Mohd Azrul Ariff Raja Azlan told a Malaysian court Monday.
Kim, half-brother of North Korean leader Kim Jong Un, was allegedly poisoned with VX nerve agent at Kuala Lumpur International Airport in February on his way back to his home in the Chinese territory of Macau.
Security footage showed two women, 25-year-old Indonesian Siti Aisyah, and 29-year-old Vietnamese citizen Doan Thi Huong, walking up behind Kim and rubbing their hands on his face.
Malaysian authorities claim the pair were trained by North Korean agents to swab Kim's face with the nerve agent. On Monday they pleaded not guilty to murdering Kim.
Representatives of Doan and Aisyah said the two women were duped into thinking that they were participating in a prank TV show.
North Korea has repeatedly and vehemently denied any involvement in the assassination of Kim.
After he was allegedly swabbed with the VX nerve agent, Kim walked to a clinic in the airport terminal, where medical assistant Rabiatul Adawiyah said she wiped a "odorless, water-like" fluid from his face with a tissue.
Nik Mohd Azrul was the first doctor to examine Kim. He told the court Kim's heart was beating quickly and his blood pressure was at a "life threatening level." Shortly after entering the clinic, Kim developed a seizure.
"I saw the patient having tonic-clonic seizure," Nik Mohd Azrul said, referring to a type of convulsion. "His eyes rolled upward and there was drooling of saliva. He was not responding to our call."
"As he was a large patient, we needed many staff to carry him together to the procedure room ... A few of us carried him together and managed to take him inside the room but unable to lift him on the bed because of his size."
The medical staff were able to stop Kim's seizure by administering adrenaline and other medicine, but then he entered a state of shock and his blood pressure plummeted.
After about an hour in the clinic, Kim was put in an ambulance to nearby Putrajaya Hospital, but the 45-year-old died en route.
High profile trial
Doan and Aisyah are being "charged with committing murder with four others who are still at large," according to a statement by prosecutors. Under section 302 of the Malaysian criminal code, a guilty verdict carries a mandatory death sentence.
Prosecutors say the pair knowingly smeared "poisonous liquid" on Kim's face, resulting in his death. They said Doan and Aisyah, along with the four unidentified perpetrators still at large, had a "common intent to kill the deceased."
In the months since Kim's death, both women have insisted they did not know their actions would kill the man. Two people who spoke to Aisyah while she was in custody said she believed the was rubbing a substance similar to baby oil or a lotion on Kim's face, as part of a prank.
Aisyah's father, Asria Nur Hasan, told CNN in Indonesia his daughter would not have committed the murder "if she was not used by someone."
"She will be proven innocent. She wouldn't harm anyone, not a child, let alone someone so powerful like that," he said.
The trial, one of the highest-profile court cases in Malaysia in decades, is likely to last for months and will be monitored closely for any insight into how North Korea and its security service operates. One of Huong's lawyers said he did not expect the defense to begin presenting its case until some time next year. Prosecutors have said they will call multiple expert witnesses to testify to the women's guilt.
"Doan looks forward to the trial where her innocence will be established," her lawyer said.