Police said the four were found dead next to the highway in the Panchrukhi area, two on either side of the highway, on Sunday.
After the autopsy, Narayanganj General Hospital’s doctor Md Asaduzzaman told the media that the wounds were inflicted by firearms and a shotgun was used to kill three of them.
They were killed sometime in the night, he added.
One of the dead has been identified as Lutfor Rahman Molla, 37, a driver from Rampura in Dhaka, by his wife Reshma Begum.
She could not identify the three others.
Reshma said her husband went out for a trip on Friday night and had been missing since then.
Police believe the killings were ‘gangland violence’.
Abdullah Al Mamun, additional superintendent of police, said they seized bullets, two pistols and a microbus from the scene.
“Our initial investigation, which found pistols and bullets at the scene, suggests that an altercation between gangs or criminals may have led to the deaths,” the police officer said.
He also said the law enforcers were trying to find out the owner of the microbus by using its registration number.