Three young boys were found dead Wednesday morning inside a vehicle parked on a Los Angeles street and their father is in critical condition.

Law enforcement sources told NBC News the children were the victims of a triple homicide perpetrated by their father, who then stabbed himself in the chest. None of the victims have been identified, but the boys were between 8 and 12 years old, according to KTLA.

"These are horrific incidents," LAPD Police Chief Charlie Beck said. "These are incidents that scar not only a community but the first responders."

The children had injuries consistent with a stabbing, according to KABC. LAPD Detective Meghan Aguilar said a knife was recovered at the scene.

Police responding to a report of an assault with a deadly weapon at 7:15 a.m. found the victims in a silver Nissan parked across the street from Dolores Huerta Elementary School in South Los Angeles. The three children appeared to be elementary-school aged, according to Aguilar, however, they did not attend Dolores Huerta. A passer-by reported the incident to police, LAPD Officer Jack Richter told the Associated Press.

Two of the children were already dead when police arrived, KABC reported, and the third died a short time later.

Cops are not searching for additional suspects, NBC reported. The biological mother of the three children is believed to be deceased, but cops think they have a step mother, KTLA reported.