Anne Arundel County Police identified the man as Kelly Brian Thompson, 33, who lived in a Wood Street rowhouse. They said he first shot and killed his wife, Nina Thompson, 34, and her 15-year-old twins, Taishawn Pugh, a girl, and Treshawn Pugh, a boy.
He then texted an agitated message to his mother, who called police and went to the house around 9 a.m., police said. As she and the police stood outside the Wood Street residence, they heard the self-inflicted gunshot that killed Thompson.
"Right now all indications are that this was a murder suicide — that the male shot and killed the other three persons and then shot himself as the officers were talking to his mother," a county police spokesman, Lt. J.D. Batten, said.
On Sunday evening, groups of neighbors stood outdoors and watched police officers and detectives exit and re-enter the Thompson house. Its porch light remained lighted. Neighbors recalled Thompson as a "quiet guy" who went out of his way to help others.
"We had heard that he may have lost his job but we also heard he got another one. All this. It just doesn't add up," said Steve Nichols, who lives three doors away from the Thompson home. "He was the kind of guy that if you had a problem, he was there to help you."
Nichols stood in his front yard Sunday evening with his wife, Sarah. They said they heard no shots because their television was on and air conditioners were running.
"Nina was a part-time nurse. She was also an awesome person," Sarah Nichols said.
The Nichols said that Thompson had owned a motorcycle and that the two neighbors had discussed the sale of a Kawasaki Jinxer that Nichols owns. They said that the Thompsons had recently brought home a puppy, which had become a center of attention on their side of the street.
The Nichols said the slain twins, Taishawn and Treshawn, were polite and respectful to their neighbors along Wood Street.
"They were the type of kids who said 'Yes, Sir' and 'Yes, Maam' to you on the street," said Sarah Nichols. She said she thought the twins were tenth-graders at North County High School.
The Nicholses described their neighbors as "quiet people" who "who looked out for others."
They also said that many people in the neighborhood own guns.
"I knew he had a gun," Steve Nichols said. "There aren't too many people around here who don't have guns. The city line is just a couple blocks away."
Neighbors said that later in the day an animal control worker came and removed the Thompson's puppy.
In a news release, Anne Arundel County police said that Thompson is not the biological father of the twins. Police said they arrived in the 600 block of Wood Street a few minutes before 9 a.m. They also said there is no indication any other persons were involved in this incident. The Anne Arundel County Police Department's Homicide Unit is investigating.