Thomas Mortimer IV Left Note at Crime Scene, Reads "I Murdered My Family," Says DA

WOBURN, Mass. (CBS/WBZ/AP) Thomas Mortimer, the man accused of slaying his wife, mother-in-law, and two young children, allegedly left behind two notes taking credit for the grisly quadruple homicide.

PICTURES: Mortimer Family Murder

Middlesex District Attorney Gerry Leone claims the 43-year-old wrote two identical letters found in his suburban Boston home. They read: "I did these horrible things. What I've done was extremely selfish and cowardly. I murdered my family."

Mortimer was captured Thursday after leading police on a brief manhunt that ended with his arrest in northwestern Massachusetts.

The suspect has been charged with four counts of first-degree murder in the deaths of his 41-year-old wife Laura Stone Mortimer, his 64-year-old mother-in-law Ellen Stone, his 4-year-old son Thomas "Finn" Mortimer V, and his 2-year-old daughter Charlotte Mortimer.

The victims are believed to have been bludgeoned to death, prosecutors said.

District Attorney Leone added that there were signs Mortimer had attempted suicide before he fled the family's Winchester home.

PICTURES: Mortimer Family Murder

The bodies were discovered Wednesday after a concerned family member who could not get in touch with the family called police.

Firefighters were dispatched to the Winchester residence and broke down the door revealing the horrific crime scene.

Mortimer had fled the scene, but was tracked down in Bernardston after a man who had seen Mortimer's SUV on the news called police.

Although police are still exploring possible motives, Mortimer's mother mentioned to CBS affiliate WBZ that her son and his wife had been going through a difficult period in their seven-year marriage.

Complete Coverage of Thomas Mortimer IV on Crimesider