Investigators have no idea why a Pennsauken man shot three of his sons, killing two of them, and then set his house on fire before police shot him dead.

Officials hope the surviving son will recover from his wounds and offer some insight into what triggered Thursday night's killing shooting spree by Alfred Moton, 54.

Slain were his sons Alfred, Jr. 18, a freshman at Rowan University and 2010 graduate of Camden Catholic High School; and Stephen, 14, a student at a Catholic elementary school.

Charles Moton, 16, a junior at Camden Catholic who had been shot in the chest, is in critical but stable condition at Cooper University Hospital in Camden.

The Camden County Prosecutor's Officer said Pennsauken Police reported no calls to the Motons' Royal Avenue house until Thursday night and had "no prior experiences with the family that might explain this incident."

Financial problems did not appear to be an issue, officials said.

But in a Facebook posting in January, Alfred Jr. suggested his father harbored apocalyptic fears.

"My dad is talkin about how the H1N1 shots are a set up for 2012, just like in I AM LEGEND, and the he's talkin about how the government is makin a DEATHSTAR to destroy earth to regular the population, gawd he's so crazy, nuffin gonna happen anyway lmao," the post said.

I Am Legend is a film starring Will Smith as the last person alive in Manhattan after a virus kills off most of the world's populations and turns survivors into monsters.

The bloody rampage unfolded at 10:35 p.m. Thursday when police responded to a report of a person down in the street and found Charles wounded on Beacon Street near Browning Road.

Police also found Alfred Jr. fatally wounded on nearby Henwood Avenue, officials said.

Dispatchers then received a report of a fire at 4434 Royal Avenue, which is around the block from the intersection of Beacon and Browning. Police arrived and found Moton in the rear sunroom "with a gun, a lighter, and a can of gasoline," said Jason Laughlin, spokesman for the prosecutor's office.

Moton charged at three officers and they opened fire, killing him, Laughlin said.

Stephen was found dead in the house along with an an elderly man, who was not wounded but taken to Cooper University Hospital to be monitored, Laughlin said.

The mother of the boys, a nurse, was at work at the time of the shooting, officials said.

Laughlin said the two-story brick house was gutted by the fire.

A neighbor, Abe Stevens, 64, said the family who lived in the house included a father and mother, three sons, and a grandparent.

Stevens said he was going to sleep when he heard two gunshots and someone screaming. He said he looked out his window and saw a young man run out of the burning house, leap over a tall fence and disappear.

Stevens said that the next time he looked out, he saw police in the backyard yelling at someone to "put it down! Put it down!" and then he heard about eight or nine gunshots.

Laughlin said it appeared that the victims were shot in the house and the two found on the streets fled before collapsing.

At Camden Catholic High School, Principal Thomas J. Kiely informed students of the shooting during his morning closed-circuit television broadcast.

He said the school's president emeritus, Monsignor Andrew E. Martin, led the student body in prayer.

Kiely said counselors were in the school, including some from Catholic Charities, to assist students who need help.

"This is terrible, a tragedy," Kiely said.

Staff writer Bob Moran can be reached at 215-854-5983 or bmoran@phillynews.com. Staff photographer April Saul contributed to this article.