At about 12:30 a.m. police received a call from a 45-year-old woman who said her boyfriend had stabbed her brother inside the couple's apartment in the 1900 block of Barrett Avenue.
Police found the woman's brother, a 37-year-old Richmond resident, suffering from a stab wound to his neck, Gagan said.
Police arrested the woman's boyfriend, 41-year-old Raymond Ratcliff, for assault with a deadly weapon, Gagan said.
The two men had reportedly been arguing about housekeeping and about how Ratcliff treated the victim's sister, police said.
The victim was last reported to be in serious but stable condition after being airlifted to John Muir Medical Center in Walnut Creek, police said earlier today. There were no updates on his condition.