The deceased was identified as Zahidul Islam Mintu, 45, son of Sardar Abu Bakkar and a local activist of Jubo Dal at Shibpur village in the upazila.
Shamim Ahmed Khan, officer-in-charge of Kachua Police Station, said Mintu had a family feud over his double marriage.
On Monday night, 10-12 people stormed into his house and beat him mercilessly.
Later, they stabbed him indiscriminately, leaving him critically injured.
Mintu was taken to Khulna 250-bed Medical College and Hospital where doctors declared him dead, reports UNB.
Police are trying to arrest those involved in the killing, said the OC.