An explosion that killed a man and destroyed three flats was "not predictable or preventable", a report has found.
Guido Schuette, 46, died in the blast in Gibbs Crescent in Oxford on 14 February last year.
Oxfordshire Safeguarding Adults Board said neither police nor mental health services could have stopped Mr Schuette, even if it was intentional.
It said he had a "long-running" dispute with a neighbour in a flat above.
In the days before the explosion, on 10 February, Mr Schuette was visited by police after the neighbour said Mr Schuette was "shouting and banging", the report said.
The caller said Mr Schuette had threatened to set fire to the place the previous night, but she did not know if he was joking.
Officers entered his home at 07:05 GMT and found Mr Schuette seated with two knives, which were removed, and he was restrained after he lunged at officers.
A "thorough" mental assessment of Mr Schuette was carried out, the report said, but it was decided he did not need hospital admission, and his case should be managed in the community.
Police had also carried out a "proportionate search" of his home but did not find evidence of stockpiled fuel, the report said.
A follow-up visit on 11 February found Mr Schuette to be "relaxed" and a check call was made on 12 February, when he complained about his neighbour's loud music.
A "keying error" in the electronic system meant no contact was made on 13 and 14 February.
The report said he purchased £23 of petrol at 14:22 GMT on 14 February and at 15:50 he visited a neighbouring flat, in distress, and said no-one was listening to him about his neighbour.
The explosion happened at 16:40 and fire investigators said it was "probably accidental" due to an unknown source of ignition.