The step-grandmother of a 4-year-old boy who had been missing for three days was charged with murder Saturday after leading police to his body in the wooded foothills of the Cascades (search).

Matal Zachery Sanchez (search) was reported missing Wednesday afternoon from his home in the Portland suburb of Milwaukie, where he lived with his mother and step-grandmother, Christine Coffman (search).

He was last seen about the same time Coffman had left the home to run an errand, Officer Kevin Krebs said Saturday.

"Naturally, people thought maybe he's with grandma," Krebs said. When Coffman returned without the child, police began to question her, Krebs said. He said Coffman's shirt was stained but declined to say if the substance was blood.

Police did not immediately say how the boy died but a medical investigator determined the cause of death was homicide.

"There is no indication that this was an accident," Krebs said.

Coffman, 43, was arrested Saturday and was being held at the Clackamas County Jail without bail. Police had impounded her car two day earlier, and investigators asked for the public's help in tracking the car's movements on the afternoon the boy disappeared.

About 70 people, including FBI agents, had searched for the boy after he was reported missing. Dogs and an Oregon Army National Guard helicopter also were used in the search.

Asked why Coffman didn't immediately lead police to the boy's body, found about 25 miles from his home, Krebs said "everyone would like to know that."

"It's going to be a long process before all the details come out," he said.

Coffman was charged with aggravated murder, which allows prosecutors to seek the death penalty if they choose. Her first court appearance was set for Tuesday.

At the family's home on a cul-de-sac, the street was cordoned off with yellow police tape. A toy moose, several teddy bears, flowers and balloons formed a makeshift memorial beneath a street sign.