Police respond to domestic calls daily, but the one they showed up to in Highland Park Saturday caught them off guard.
"They see 4 children come running out covered in blood," said Sergeant Frank Preciado with LAPD.
"So, obviously the mindset of the officers is we have an active shooter. The brother that came here was uninvited. Things went sideways, and he armed himself with a kitchen knife attacking his brother and mother."
Sgt Preciado says the man stabbed both of them. Meanwhile, four kids in the house, ages 4-7, went to the window of the second story apartment and screamed out for help.
"We could hear them from inside our house," said a neighbor who lived across the street.
Police say the suspect's brother, "went into the bedroom, and retreived a handgun and shot his brother."
Police couldn't confirm what caused the confrontation, though a man claiming to be a family member said he thought the suspect was on drugs.
"He lunges at officers, the officers take control of the invidual and start interviewing the people inside," Sgt Preciado added.
All three adults were transported to a nearby hospital, the suspect in critical condition.