A 27-year-old Alexandria man was charged with murder yesterday in the death of his girlfriend's 2-year-old son, Alexandria police said.

Mark Anthony Hines of 726 S. Fayette St. was arrested a few minutes after midnight, after a medical examiner completed a preliminary autopsy on Curtis D. Ligon, investigators said.

The cause of the child's death was not released, but an Alexandria police spokesman said that "suspicious circumstances" surrounding the death caused investigators to classify it as homicide.

The 27-month-old boy was pronounced dead at Alexandria Hospital at 12:07 p.m. Wednesday after paramedics found him in Hines' third floor apartment. Until yesterday authorities had listed the death as accidental.

The child's mother, Annette Ligon, 20, had been living with Hines in the Fayette Court Apartments near the intersection of Rte. 1 and the Capital Beltway for the past three months, according to Betty Hines, 25, the suspect's sister.

"They had their arguments like everybody," she said, but her brother "loved that little boy like his own."

"I knew him Hines for 15 years," said Randolph Dixon, the resident manager at the 51-unit Fayette Court Apartments. "He was clean-cut, quiet . . . spent about six years in the Army."

Betty Hines said that after her brother "traveled the world with the Army," he began working the night shift as an operator for the Alexandria Sanitation Department.

Juvenile and Domestic Relations Judge Joseph L. Peters released Hines on $50,000 bond after a hearing yesterday afternoon. A preliminary hearing is scheduled for Feb. 25.

"It's a shock," said Cindy K. Clarke, the executive director of Micah Housing Inc., owners of the apartments where the child died. She said Mark Hines came into her office about noon Wednesday to use the phone and the fire department and an ambulance arrived a few minutes later.

"He was such a cute child," Clarke said of the boy. "Before the cold weather came, he'd be out playing on the lawn as happy as could be."