The sound of gunshots in a residential neighborhood in Northeast Baltimore prompted an anonymous 911 call to police early Tuesday. Three city officers responded to a rowhouse on Nicholas Avenue, repeatedly knocked on the door and windows, and found nothing amiss.

So they left.

Less than 90 minutes later, someone set the house on fire, and firefighters found the bodies of two men and a woman who was critically injured. Each victim, police said, had been shot, at least one in the head, and the woman died later at Johns Hopkins Bayview Medical Center.

"All he did was work and come home," said Joe Scruggs, a neighbor who said he had known the owner of the burned-out house, Billy Ray Lovitt, for decades. Lovitt's daughter came to stay with him a few weeks ago, Scruggs said, while he recovered from surgery. A folded walker, tarnished by smoke, had been tossed into the front yard with other debris from the blaze.

City police did not release the names of the victims on Tuesday, but a police spokesman said the dead are the 58-year-old homeowner, his 36-year-old daughter and her 27-year-old companion. Lovitt's sister-in-law, Irish Lovitt, said that the woman living with him was not his biological daughter, but that he raised her.

Baltimore police spokesman Anthony Guglielmi said the department is examining how the patrol officers responded to the call and whether they acted appropriately by not forcing their way inside the house, located off Belair Road near Herring Run.

Police acknowledge there is a possibility that the killer was still inside the house when police knocked on the door, and that the woman was inside and still alive at that point. The anonymous call about gunshots came in at 4:33 a.m., the officers arrived at 4:36 a.m. and left at 4:59 a.m., Guglielmi said.

Scruggs, who lives right across the street from Lovitt's home, went out for a walk about 5 a.m., he said, but did not notice anything strange in the neighborhood. It wasn't until 90 minutes later that someone called 911 again, this time to report a fire.

Firefighters pulled up to the 4300 block of Nicholas Ave. at 6:37 a.m., about two hours from the time the call for gunshots had been made. Police said they recovered physical evidence and that an accelerant was used to start the fire, but no suspects have been identified.

Guglielmi said the officers "made multiple attempts" to attract attention by banging on the front door and windows of the brick home. He also said the officers canvassed the neighborhood and knocked on doors of neighbors in an attempt to speak to them.

The spokesman said the review will include determining whether the officers could have forced their way inside the house, citing exigent circumstances that allow police to conduct warrantless entries in emergencies, in life-threatening situations or when they think evidence of a crime is being destroyed.

"We're looking at it to determine if we did everything we could," Guglielmi said. He noted that the officers did spend more than 20 minutes at the scene.

Michael Milleman, a law professor at the University of Maryland School of Law, said that a report of shots fired would justify police's forcibly entering the home. At the very least, he said, it would be sufficient to obtain a warrant for police to go inside.

But retired Baltimore Circuit Judge Joseph H.H. Kaplan said that the police officers would have had to have seen suspicious activity or heard what he called "dangerous sounds" from inside the house to go in without a warrant.

"There would have to be something they saw or heard themselves," Kaplan said.

Police said on Tuesday that they know of no suspects or motive in the killings. Guglielmi said the owner does not have a criminal record, but others in the house had prior contacts with law enforcement that are being investigated as part of the investigation.

Authorities said one man was found on the first floor, and the second man and the woman were found on the second floor. Baltimore Fire Chief James S. Clack said the one-alarm fire was confined to the first-floor rear of the two-story home, and was quickly brought under control.

A firefighter at the scene said there were two separate fires, one in the living room and another in the dining room.

According to online property records, Lovitt has owned the home since 2007, and the address is listed as a principal residence.