DAMASCUS, Md. (AP) — A Maryland man and military combat veteran has been charged in the fatal beating of his 3-year-old son who was adopted months earlier from South Korea, police said.

Brian Patrick O'Callaghan, 36, of Damascus, has been charged with first-degree murder and child abuse resulting in the death of the boy earlier this month. He was ordered held without bond during a court appearance Tuesday. O'Callaghan, a former Marine, did not commit any crime and is a National Security Agency worker who specializes in Korea, his attorney said.

Investigators were called to Children's National Medical Center in Washington on Feb. 2, where police say the boy's injuries, including bleeding in the brain and a skull fracture, indicated he had been beaten. The boy died the next day of multiple blunt impact injuries, which O'Callaghan could not explain or account for, according to police charging documents.

Montgomery County police say O'Callaghan told investigators he had been caring for the child while his wife was out of town when the boy at one point fell backward in the shower and hit his shoulder. The following day, O'Callaghan said, he put the boy down for a nap. But when he went to check on him, the child had mucus coming from his nose and began vomiting while unresponsive after he was picked up, police said.

O'Callaghan said he took the boy to a hospital emergency center. Doctors became concerned that the child might be brain dead because of internal bleeding in the brain and hemorrhaging in the eyes, police said.

O'Callaghan's lawyer, Steven McCool, called the allegations of murder "unfounded." He said he disputes that the child suffered a skull fracture or multiple injuries to his head.

"My client, a decorated Iraqi war veteran, is grieving the loss of his son while fighting what ultimately will be shown to be unfounded charges," McCool said.

O'Callaghan's lawyer identified him as an ex-Marine and combat veteran who received awards for his service in Iraq and Kosovo. He said O'Callaghan now specializes in Korea at the NSA. The NSA did not immediately return an email seeking comment.

Police identified the child as Hyunsu O'Callaghan. An obituary posted on the website of the Frederick News-Post spelled the boy's name as Madoc Hyeonsu O'Callaghan and said he was born in South Korea and had joined the family last October. The child was described in the obituary as a "smiling, content, and loving son and brother."

"He loved his dogs, his big brother Aidan, and anything his parents made for him to eat. He wasn't dealt the simplest hand in life, but he found something to love in it every day," the obituary said.