One of the deceased was identified as Abdur Razzak, 40, from Paikpara village in Sadar upazila. The identity of the second victim has yet to be confirmed.
According to police, the incident took place near the Panchthakuri area of the Jamuna River.
Acting on a 999 emergency call on Sunday night, law enforcement recovered one body floating in the river and another injured individual in critical condition.
The latter was taken to Shaheed M Mansur Ali Medical College Hospital, where he was declared dead.
Inspector (Investigation) Ahsanuzzaman of Sadar Police Station confirmed that the bodies are currently being kept at the hospital morgue.
Md Rafikul Islam, officer-in-Charge of Sirajganj River Police Station, said that three cows—two belonging to Abdul Mannan and one to Azizul Haque, both from Shonapcha village in the char area of Bogura—were allegedly stolen on Sunday night. While being transported by boat, the suspects were intercepted and beaten by a mob, leading to their deaths.
Police have arrested two thieves in connection with the incident and recovered a boat and the cows, though one of the animals died, the OC said.
The thieves were identified as Faruk, 40, from Rangachuria village in Tangail, and Vikram Sheikh, 47, from Charia Kandapara village in Sirajganj Sadar upazila.
A case has been filed at Sariakandi Police Station in Bogura, reports UNB.
Meanwhile, a separate case of murder has been lodged with Sadar Police Station in Sirajganj, naming more than 100 unidentified individuals as accused.
The investigation is ongoing, police said.