SAN DIEGO - A man accused of a spate of attacks on homeless people who were asleep and in some cases set on fire has been freed from jail and has not been charged with any crimes, prosecutors said Monday.

San Diego police arrested 36-year-old Anthony Padgett on Thursday on suspicion of murder, attempted murder and arson and identified him as the sole suspect in all four attacks.

The San Diego County district attorney's office said Monday that police did not submit the case for prosecution. It says the investigation continues into the attacks on four homeless men over four days last week - three of whom died.

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Police have scheduled a 3 p.m. news conference to discuss Padgett's release.

Dionicio Derek Vahidy, 23, died on Sunday, four days after he became the fourth and final victim in the attacks, police said. Vahidy had been in grave condition since Wednesday and had not been expected to survive.

Vahidy was from San Diego and was homeless, police said. He was attacked at an apartment complex downtown, police said. A witness pulled away a burning cloth that the attacker put on him before fleeing.

In the days before the attack on Vahidy, two other men were killed and a third was severely injured. Three victims were sleeping alone, and two were set on fire.

The violence began July 3, when police found the badly burned remains of Angelo De Nardo between Interstate 5 and train tracks. The 53-year-old died before his body was set on fire.

The next day, officers responding to a 911 call found Manuel Mason, 61, with life-threatening injuries to his upper torso. A few hours later, police discovered the body of Shawn Longley, 41, who bled from the upper torso and died.

Then on Wednesday came the attack on Vahidy.

Padgett committed a nearly identical crime six years ago, admitting to setting a man on fire and leaving him badly burned in a supermarket parking lot in the San Diego suburb of National City.

CBS News 8 in San Diego reported that Padgett was convicted of mayhem and sentenced to four years in prison for a 2010 attack on his 49-year-old homeless friend.

He said in a note to a judge at the time that he was drunk and high on drugs when he did it and had only meant to scare the victim, who he knew.

In the note, Padgett also called himself a "homeless citizen," asks Jesus to forgive his sins and expresses remorse for the victim, saying, "I'll never be so stupid again."