A mother and her 20-year-old son were found shot to death in their Fort Washington home early Thursday, Prince George’s County police said.

Officers went to the single-family home in the 11800 block of Hickory Drive after Frank Harris Jr. called 911 from inside the house about 4:30 a.m., police said. They said Harris’s wife, Patricia, 56, and son, Frank L. Harris, were dead on the main level. Each had been shot multiple times.

Prince George’s police spokesman Julie Parker said there were no signs of forced entry. No arrests had been made as of Thursday evening, and law enforcement sources said investigators are exploring multiple theories.

Residents on the block describe the Harrises as polite people who have lived in their two-floor brick home in the quiet, upscale neighborhood for at least 15 years.

Frank Harris Jr. works in landscaping, said Gary Ray, who lives across the street and sometimes helped Harris fix the work trailer he kept behind his home. The elder Harris was a Boy Scout leader for the troop at Fort Washington Baptist Church, and Frank L. Harris was an Eagle Scout, said Mark Holt, a family friend.

Holt, also a Scout leader for the troop, said the Harrises were “just really, really solid, stable people.” He said he had last talked to the younger Harris a few months ago, when the young man had made a pitch to him to buy some Cutco cutlery.

“Just the fact that it was them is what people are shocked about,” Holt said. “They were just real friendly and just really nice people. Everybody liked them.”

Parker, the police spokeswoman, said Frank Harris Jr. has been cooperating with detectives.

Monique Ray, Gary Ray’s daughter, said the younger Harris graduated from Friendly High School in 2008 and lived with his parents. She attended high school with Harris and said he was polite and tended to keep to himself.

Gary Ray said that Patricia Harris has an adult son from a previous marriage and that he visits the home a few times a year.

“It’s irritating that it’s so close to home,” Monique Ray, 20, said. “This is really a drama-free neighborhood.”

The Harrises attended services at Fort Foote Baptist Church nearly every week since around 1990, said their pastor, the Rev. Joseph W. Lyles. “Quiet and unassuming,” the Harris men regularly came to church in suits, shirts and ties, and the mother came in elegant dresses, Lyles said.

Lyles said he had heard of an incident at the Harris home when a colleague at the church, David McElveen, called him about 9 a.m. McElveen, the family deacon for the Harrises, had been at the scene Thursday morning, neighbors said.

“One wouldn’t think that this kind of tragedy would come out of that household,” Lyles said.

Staff researcher Magda Jean-Louis contributed to this report.