Officer-in-charge of Lushtia model police station Kamruzzaman Talukdar said the father and son were going to KNB Agro Industries while on the way a truck hit their motor-cycle killing Mehedi on the spot.
Sharif Uddin is admitted to Kushtia Hospital in a critical condition, OC said.
In Panchagarh, a housewife was killed while her husband and two children injured after a motorcycle collided head-on with a truck in the municipality area of Debiganj on Sunday.
The deceased is Suborno Rani, 32, wife of Birenranath Roy.
Officer-in-charge of Debiganj police station Hasan Sarkar said the family was going to celebrate Durga Puja in Debiganj town when their motorcycle hit a truck, killing the woman on the spot.
Roy and the couple's children were also critically injured in the accident, he said. They have been admitted to Rangpur Medical College Hospital in critical condition, he added. Police have seized the truck but its driver managed to flee, OC said.