Description

The "saucer" pursuit starts at 3:50.

The Atlas D missile tests took place in 1964 at Vandenberg Space Force Base. One of the missiles was shot down by a UFO that fired 4 beams like shown in the 3D reproduction below.
https://youtu.be/jjeJy_5WiQ4?t=590

This is reported by Lt Bob Jacobs who saw the original film before parts of it were cut by some men in civilian clothes from an unknown agency. He describes the events and UFO shooting in this testimony :

https://youtu.be/M5-ul2rgZT0?t=18

The video shown above on the post seems to show a saucer shape locking on at 3:50 and following one of the missiles of that series of tests exactly like Bob says, but im not sure if this video was taken from the missile that was shot down before the saucer fires at it, or from another test during the same period.