The group had gathered in the woman’s residence in Lund in southern Sweden to celebrate her 70th birthday which was coming up the following week.
But the celebration quickly turned tragic.
“We believe that the suspect is the perpetrator,” Per Lidehäll with the police told the local Sydsvenskan daily.
At around 1pm on Saturday, the woman’s 40-year-old son allegedly attacked his mother with a knife, in front of friends and family.
She was taken to hospital, but her life could not be saved.
Shortly after the fatal stabbing, police arrested the woman’s son on suspicions of murder, with an alternative charge of manslaughter. The reason behind the attack remains unknown.
Guests at the birthday celebration have been interviewed about the incident, and more interrogations will take place on Sunday.
According to Sydsvenskan, the victim and her son were registered at the same address, while the Aftonbladet newspaper received information that the son was recently under investigation for being placed in psychiatric custodial care.