Authorities on Wednesday reluctantly released the first installment of police video from the deadliest mass shooting in modern U.S. history, the massacre of 58 people last year at an outdoor music concert at the Mandalay Bay Resort and Casino in Las Vegas.

Sheriff Joe Lombardo, chief of the combined Las Vegas police and Clark County sheriff's offices, strongly objected to releasing hundreds of recordings and documents from the investigation but said he had no choice under a court order obtained by news organizations.

Lombardo apologized to Las Vegans in advance on Tuesday, predicting that the material would unnecessarily force them to relive the night of terror and strain the department's resources as officers were diverted to sift through the documents and recordings.

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"We believe the release of the graphic footage will further traumatize a wounded community. For that, we apologize," Lombardo said Tuesday.

He told reporters Tuesday that nothing in the extensive trove of materials offers any insight into the motive of Stephen Paddock, 64, who was armed with 23 firearms, as well as explosives and thousands of rounds of ammunition, when he opened fire from the 32nd floor of the casino on the night of Oct. 1 before he killed himself.

The first police body camera videos released Wednesday run about 9½ minutes combined and shed little light on the investigation. They were shared with NBC affiliate KSNV and other local news organizations and are only the first of what will be numerous releases over the coming months, estimated to include 750 hours of video alone.

Two of the clips record officers entering Paddock's hotel suite, blasting through doors, conducting reconnaissance and discussing cameras they found in the suite and on a cart outside the door, which Paddock is believed to have placed to monitor anyone approaching his room.

A third clip records an officer walking through the hotel lobby and warning people to leave.

The fourth records an officer walking through a hotel hallway warning colleagues to "watch out for blue on blue" — that is, be aware that other officers are present. Later in the clip, the officer opens the door to another room and alerts its residents that an gunman is in the hotel.

There is no video from the officer who breached the door to Paddock's suite and was the first to enter it. His body camera was off or wasn't working for reasons police have declined to discuss.