Officers investigating the death of Patrick Marcelin's six-year-old son at 61 Devon St. on Thursday were unable to keep Marcelin from stabbing himself to death when they arrived at the apartment where he'd been staying on Saturday, the Boston Police Department reports.

According to police, the boy was in cardiac arrest when first responders arrived at his home around 9:30 a.m. on Thursday, but that the exact cause of death remains under investigation. Then, police say:

"Detectives learned that the boy had been staying with Marcelin, his father. The father was no longer present at the residence and detectives began searching for him in order to interview him in connection with their ongoing death investigation.

"Last night, detectives learned from a family member that Marcelin had made statements expressing an intention to harm himself, and the search for his whereabouts intensified.

"This afternoon, in the course if the investigation, detectives pinpointed Marcelin's location inside an apartment at 815 Morton Street. Detectives knocked on the door at about 4:30 PM. Marcelin answered the door with a kitchen knife in his hand and began to injure himself. Placing themselves in harm's way, detectives made heroic efforts to disarm him, took the knife away, and called for medical assistance. Marcelin was rushed to Boston Medical Center, where he was pronounced dead of his self inflicted injuries."

Police say they do not expect charges against anybody in the case.