He killed his first victim in the second floor of a private hospital, before hitting the streets to kill five others and injure one.
A resident of Macchgar near Ballabhgarh, Dhankhad also attacked the policemen when they tried to nab him.
He had joined the Army in 1999 as a lieutenant and taken retirement on medical grounds in 2003. He then joined the Haryana Agriculture department as an assistant development officer in 2006, a police spokesperson said.
His first victim was a woman named Anjum who was an attendant of a person admitted in the ICU of the hospital. She was sleeping on the second floor where the accused managed to gain entry, Palwal Superintendent of Police Sulochana Gajraj said.
The incident was recorded on a CCTV camera and the accused can be purportedly seen coming inside the doors wearing trousers and a sweater and carrying the rod.
He then went to Agra Road intersection where he killed three more people. Then a little farther, he killed two others by repeatedly hitting them on the head.
Gajraj said as soon as the police received information, they started sending people, who were either sleeping or working outside, indoors.
She said checkpoints were set up in the town, which is 80 km from Delhi. "When we zeroed-in on him, he was searching for another target and almost had his seventh victim as he had injured him," she said.
He was arrested around 7 am when he was roaming in a street near a private hospital in Palwal, the SP said, adding that thick fog in the town had reduced visibility making it easy for the accused to target the victims.
Dhankar tried to resist arrest and even assaulted the policemen before being overpowered, she said.
The SP said that Dhankar appeared to be mentally ill. However, doctors would be able to throw more light on this, she added.
"He appeared to be mentally ill and looked highly aggressive. Preliminary investigations have revealed that he had strained relations with his wife and two children," she said.
Deputy Superintendent of Police Abhimanyu Lohan said prima facie it seemed that he carried out the killings without a reason.
A high alert was sounded in the city, the police spokesperson said.
The spokesperson said Dhakhad got married 10 years ago and separated from his wife four years later. Dhankad was the youngest of five brothers.
His brother, Chandrapal, claimed that Dhankhad was mentally ill and was being treated by a doctor in Muradnagar, the spokesperson said.
He claimed that his brother had completed MSc from Haryana Agriculture University in Hisar where he was one of toppers.
A doctor at the hospital at Faridabad where the accused was brought by the police told reporters that he was unconscious at the time he was wheeled in.