A man shot and killed his ex-girlfriend and her brother before turning the gun on himself in a murder-suicide in Vista early Monday morning, the San Diego County Sheriff's Department (SDSO) confirmed.

Around 10:45 p.m. Sunday, deputies responded to a report of a fight at a home on the 1400 block of Phil Mar Lane in Vista. When they arrived on scene, the people inside the residence refused to cooperate with deputies, SDSO said.

The location of the neighborhood is northeast of State Route 78 and southwest of S Santa Fe Avenue.

At the same time, deputies arrested a man as he was driving away from that home. He told investigators that he had sustained injuries in an altercation with an ex-girlfriend's brother at their house.

According to the sheriff's department, he was taken into custody for driving under the influence of alcohol but due to his injuries, he was released around 1 a.m.

Hours later, investigators were called to the same home on Phil Mar Lane just after 5:30 a.m.

A friend of someone living at the home said she had arrived to find three people dead inside the house.

"They are in different rooms throughout the house," Lt. Greg Rylaarsdam said.

The man appeared to have shot and killed his ex-girlfirned and her brother before killing himself after returning to their home following his release, the sheriff's department said.

The woman, 52 and her brother, 53, were not identified pending family notification.

SDSO said the suspect was a 52-year-old man.

Longtime resident Deanna Fortin said the community is in shock.

“There’s never been anything remotely like this here in 29 years. It’s scary," Fortin told NBC 7.

3 ppl found shot dead in Vista home on Phil-Mar Ln this morning. 2 Men 1 woman no suspects outstanding: Sheriffs dept @nbcsandiego pic.twitter.com/qfrSJn6sD8 — Chris Chan (@ChrisChanSD) March 13, 2017

Deputies said they were in the very early stages of the investigation. They are actively seeking witnesses.

The Medical Examiner's office will determine the cause of death. The investigation is ongoing.

Anyone with information is asked to call Crime Stoppers at (888)580-8477 or the Homicide Detail at (858)974-2321.