Police said they received dozens of calls at around 5:30 p.m. about a violent disturbance in an apartment in the 3600 block of 42nd Street.
When officers arrived, they found the victim bleeding uncontrollably from at least 10 stab wounds, San Diego Police Department Lt. Manny Del Toro said.
Medics took the man to a trauma center, where he was later pronounced dead, Del Toro said.
The assailant, who remained at large Tuesday night, was described as a 25-year-old Latino, 5 feet 6 inches tall, with a thin build.
Police believe the attacker may have been the victim's son.
"At this time we don't know if he left with the murder weapon. If he did, it would be a stabbing instrument of some kind, possibly a knife," Lt. Manny Del Toro said. "And as far as any drug use, we don't know. Obviously this was a very violent attack. It is possible"
It was unclear what led to the assault.