A man died and a woman and two children escaped after a major fire started deliberately at a house in Dudley.
The man in his 40s, who has not yet been named, is believed to have started the blaze. Officers are also investigating reports of a gunshot.
A woman, aged 42, and two boys aged nine and 15 escaped just seconds before the blaze took hold.
The woman and children were taken to hospital as a precaution and later discharged.
Police were called to Wood Street in the Holly Hall area at around 6.10pm to reports of a fire.
Today, the property remained sealed off pending an examination by forensic scene investigators. They have been unable to enter the building amid fears for its structural integrity.
Det Insp Simon Astle, from Force CID said: "This was a major fire, started deliberately, which has claimed a man's life and was so fierce that the property has been left in a dangerous state.
"A woman and her two sons, who we believe were known to the man, have been left badly traumatised by what has happened. Fortunately none were seriously injured.
"All three are being supported by specially trained officers and our investigation is well underway."
Wood Street was closed for around 10 hours and nearby properties were evacuated until the situation was deemed safe.
A West Midlands Police spokesman added: "House to house enquiries have been conducted and a number of witnesses spoken to. Officers stepped-up patrols in the area on Saturday night and throughout Sunday morning to reassure worried locals.
"Detectives are not looking for anybody else in connection with the fire which started well inside the house but anyone with information which may aid the ongoing investigation should call police on 101."