Police say Melvin McMains met officers outside his Laurel apartment yesterday morning and told them, "I have sinned and killed them all."
Inside, Howard County police found the bodies of his 30-year-old companion, her 8-year-old son and the family dog.
McMains, 36, a bus mechanic, was arrested and charged with two counts of murder. Police said they had not determined a motive.
McMains was held overnight in Howard County's jail and is scheduled to have a bond hearing in District Court this morning.
McMains is accused of killing Caria A. Roth and her son, Christopher Roth, who lived with McMains at the Whiskey Bottom Apartments in the 9100 block of Bourbon Street in North Laurel. The homicides were the first in Howard County this year.
Caria Roth was found shot in the head, and Christopher had been stabbed several times, said Howard County police spokesman Gary Gardner.
Both bodies and the dog were found in the living room.
Police said they recovered handguns from the apartment, as well as an unspecified quantity of a drug they suspect is PCP.
Gardner said police were called to the apartment complex shortly before 8:30 a.m. to respond to "unknown trouble."
Police were met there by McMains, who had just walked out of his ground-floor apartment, Gardner said.
McMains, who was unarmed, then calmly told police that he had "killed them all," Gardner said. Gardner said police then entered the apartment and found the victims.
Gardner said it could not be determined yesterday whether McMains had a criminal record or a history of mental illness.
Neighbors at the complex described the couple as friendly but quiet. Residents said Roth and McMains had moved in in late August or early September of last year.
"They pretty much stayed to themselves," said Denise George, who lives in an apartment above the one where the slayings occurred. "If you saw them, you know, they would nod and say hi to you."
George said that she heard "banging noises" between 5 and 6 a.m. yesterday, "and came to find out later they were shots."
Another resident who lives above the couple said McMains knocked on her door yesterday morning and asked to use her telephone. After determining who McMains wanted to call, the neighbor offered to call police for him.
"He didn't tell me why he needed the police," said the woman, who asked not to be identified, "and I would not have guessed from looking at him. He was very calm, very coherent."
McMains has a phone listed in his name at the Laurel address. It was working yesterday evening.
Residents, who called their sprawling apartment complex "very safe," described themselves as shocked by the slayings. "I've lived here 10 years, and we've never had anything like this happen here before," said the woman who called the police.
"It seems like stuff like that couldn't happen around here," George said. "It's very shocking. You just never think that something like that will happen next door."