The Los Angeles County District Attorney's Office charged a San Marino man with murder and arson after he allegedly started a fire to cover up his wife's death.

Suspect Yoon Lai pleaded not guilty to two charges, which carry a sentence of life in prison. He's being held on a $2.25 million bail. Lai is expected to return to court on Aug. 12 for his preliminary hearing.

The San Marino Fire Department found Lai's wife, 56-year-old Irene Gaw-Lai, dead on the doorstep of the couple's home in the 2000 block of Lorain Road on Jan. 6. Firefighters said they were initially called to the house for a fire. 

"The violent death of Dr. Irene Gaw-Lai is heartbreaking and deeply disturbing," District Attorney Nathan Hochman said. "She was not only a respected physician and business leader, but a mother who deserved safety and dignity in her own home.   

In the six months since her death, the LA County Department of Medical Examiner has finished the autopsy and toxicology reports on Gaw-Lai's remains but has not determined her cause of death. The medical examiner listed her manner of death as undetermined, meaning the agency did not have enough evidence to classify how she died. 

After serving 25 search warrants, the Los Angeles County Sheriff's Department obtained an arrest warrant for Lai and apprehended him at his home in San Gabriel last week, according to the agency's Homicide Bureau. 

Detectives did not elaborate on the motive behind the alleged killing.