Thomas Mortimer IV entered pleas to first-degree murder in Woburn Superior Court for the deaths of his mother-in-law, Ellen Stone; his wife, Laura Stone Mortimer, and their two children, 2-year-old Charlotte and 4-year-old Thomas Mortimer V. He faces life in prison without parole.
Police said the victims' bodies were found in pools of blood when Mortimer's sister-in-law went to the home after her repeated telephone calls to her mother and sister weren't answered.
Prosecutors said the slayings followed marital problems between Mortimer and his wife. The children's throats had been slashed.
Mortimer, who grew up in Avon, Conn., was apprehended the next day in northwestern Massachusetts.
In court documents, prosecutors said they found a confession written by Mortimer in the house.
In the note, Mortimer said he flew into a rage after he and his wife argued over a bounced check he sent to the Internal Revenue Service, court documents said. Mortimer also revealed that his 4-year-old son witnessed the killings of his mother, grandmother and sister before he was killed himself, the documents said.
"I did these horrible things," he wrote, according to court documents. "What I have done is extremely selfish and cowardly."