A 25-year-old man was stabbed to death during a Friday evening brawl in the northern city of Kiryat Bialik.
A second man in his 40s was seriously injured in the same incident and was taken to the Rambam Medical Center in Haifa.
Police said in a statement that an investigation had been opened.
No arrests have been made although several people were said to have been involved in the fight.
In a separate incident hours earlier, a deaf and mute father of eight was shot dead in southern Israel.
According to a police statement, the man named by the Ynet news site as Salim al-Huashla, was brought with a gunshot wound to a gas station along Route 40, south of Beersheba, where he was pronounced dead by medics.
Citing an assessment held by the commander of the Negev precinct, police said he appeared to have been struck by a stray bullet that was fired as part of a dispute between rival clans in the area.
Police arrested a man in his 20s on suspicion of involvement in the shooting.