Crossbows, a knife, a sword and a hatchet were found after an armed man was killed by police, the Independent Office for Police Conduct (IOPC) says.
Armed officers were called to Surrey Quays, south London, just before 05:00 GMT after receiving reports a man armed with a crossbow was trying to get inside a property, the Met Police said.
The 30-year-old man, who was wearing body armour, died at the scene.
The IOPC believes he was known to at least one occupant in the property.
It said local police officers "unsuccessfully attempted to speak to the man, who had gained entry to the property" in Bywater Place, Southwark, "but then called for assistance from armed officers after being threatened".
"After arriving at the scene, the armed officers then entered the house where the man was shot," the IOPC continued.
"We can confirm two shots were fired from a police issue firearm, which will be subject to further analysis."
The IOPC launched its investigation after the man's death, which is standard when there is a fatal police shooting.
It has now confirmed that officers have informed the dead man's next of kin.
Police said that before his death the man was allegedly threatening to injure people in the property.
Two people inside are understood to have received minor injuries.
A number of police vehicles remain in front of a cordon sealing off the street from the main road.
Residents have expressed their disbelief that something like this could happen in the area.
Michael Leng described the shock he felt after leaving his house.
"It's fairly peaceful in this area," he said. "Nothing like this happens. It's shocking to see this sort of thing."
For those living inside the cordoned-off area, many have been anxiously watching police activity throughout the day and said they have been trying to understand why the initial confrontation happened.
Det Ch Supt Seb Adjei-Addoh said: "My thoughts are with all those affected by this incident.
"I understand the local community will be concerned at the events that have taken place this morning. We will fully support the IOPC investigation into the full circumstances of what happened."
An IOPC spokesman said investigators have been at the scene to gather evidence.
Fatal police shootings are relatively rare in the UK - just one was recorded last year.
The most recent fatal shooting by the Met Police was that of Giedrius Vasiljevas, 40, who died at his home in Dagenham, east London, in November after calling 999 to say he had loaded guns and wanted to take his own life.