Police are investigating a potential homicide in Ontario, Calif., after a resident shot and killed a drunk intruder who broke into his apartment and attacked his sleeping son.

In California, citizens have a right to protect themselves and their families, however, there are stipulations in the state.

Calif. Man Shoots, Kills Drunk Intruder Who Broke Into His Home and Attacked His Son

Police said an Ontario resident shot and killed an intruder who broke into his apartment in the middle of the night and attacked his sleeping son on Monday, June 24, 2013. (NBC Los Angeles)

“The homeowner, the citizen, has to be able to articulate or apply the appropriate amount of force that was done against them,” Ontario Police Sgt. David McBride told NBC Los Angeles, later adding that Manzano was unarmed at the time of the shooting.

Thomas Gilbert Manzano, 24, forced his way into the California residence at around 3 a.m. on Monday, according to police. Manzano had been drinking alcohol for several hours with a friend when they decided to break into an apartment they thought was vacant. They had reportedly been squatting in one of the apartments but got confused as to its location.

Manzano was first turned away from the apartment, but he allegedly threatened the resident and forced his way into the home through a bedroom window and then went after the resident’s adult son. Police say the suspect threatened the son and a physical altercation ensued.

Responding to the commotion coming from his son’s room, the father retrieved his firearm and rushed to protect his son. He then shot several rounds at the suspect.

Manzano was transported to a local hospital with serious injuries. He was later pronounced dead.

The case is now being investigated as a homicide and the district attorney will determined whether the shooting was justified, according to officials.

The resident and his son were cooperating with police.

Manzano’s uncle, “Alfonso,”  told NBC Los Angeles that the shooting was not justified.

“Just because you have a gun and its registered, doesn’t give you the right to kill somebody,” he said.