UPDATED 01/17/12 9:42 p.m.

OAKBROOK TERRACE, Ill. (CBS) — A man facing prison for heroin possession fatally shot his girlfriend, her two sons and niece as they slept in the home they shared in unincorporated Villa Park early Tuesday.

Then, as police sought a search warrant, he drove to his father’s home in Dolton and shot himself to death.

Authorities said that 42-year-old Cedric Anderson left behind a note indicating that he was despondent, but did not admit responsibility for the murder and arson in the note.

LISTEN: WBBM Newsradio’s Bob Roberts reports

The fire broke out Tuesday morning in a ranch house on Summit Avenue near Roosevelt Road in unincorporated DuPage County near Villa Park, officials said.

Authorities said they determined that 37-year-old Ursula Nailor, her sons 16-year-old Darnell Holt Jr. and 13-year-old Daniel Nailor and 19-year-old niece Dominique Robinson had been shot in their beds as they slept before the house was set afire, at about 7:15 a.m. Tuesday.

DuPage County authorities were in the process of obtaining a search warrant when Anderson killed himself. Tom Ahern, spokesman for the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, said that Anderson’s father called 911 to inform them of the suicide. Once police arrived at the home in Dolton, they found a .357 magnum revolver believed to have been used in the Villa Park shootings.

Authorities said that Anderson had been found guilty of heroin possession Dec. 29 in Maywood Court, but was free on bond pending sentencing by Judge Thomas Tucker in March. He faced up to three years in prison when sentenced.

Ursula Nailor, 37 (left) and her sons Daniel Nailor, 13 (center), and Darnell Holt Jr., 16, (right), were killed in a fire in unincorporated DuPage County near Villa Park on Jan. 17, 2012. A fourth victim, Dominique Robinson, 19, is not pictured. (Credit: Facebook photos)

Neighbors in Villa Park told CBS 2’s Dorothy Tucker the family lived in the neighborhood for about three years, and appeared to be a good family.

“A nice family – they were nice; they were friendly, cordial,” said neighbor Ann Bendara. “We weren’t that familiar. We had coffee and stuff. There were two sons and a mother, and that’s all I know about them, really. But they were very nice people.”

One woman said her son was inside the house, and was in tears as she walked away with an investigator. Three others were also sobbing as they walked away.

Almost 100 of Darnell’s friends and classmates from Willowbrook High School came to a vigil outside his charred home Tuesday night to remember him.

“I loved him,” Darnell’s friend Arthur Barhajas told CBS 2’s Dana Kozlov. “He was competitive. He was like a brother to me.”

They were also trying to understand why someone would kill Darnell and his family.

“I’ve never lost a friend this close,” another friend said.

One of Darnell’s friends said Anderson didn’t seem to be a threat to anyone.

“He gave us rides places and I just never saw him as a man who would do that,” Kiefer Provost said.

Police were guarding the house overnight. They expected to return Wednesday morning to finish collecting any evidence they might need.