Very Strange In The Skies Of Las Vegas

I'm not sure what to make this.
This evening, around 7:00 pm, I was at the dog park in Henderson, NV., by Horizon and Horizon Ridge (next to Black Mountain).
The park lies directly under the flight path of planes coming from the West, who then do a U-turn a few miles further East and then head into McCarran airport.
This evening I was watching a jet fly east over the mountain when another plane, a smaller plane, possibly a twin engine propeller plane come from the south and fly directly under or over the jet but it was only a distance of a couple hundred feet, perhaps.  In aviation terms, that is a very close call.
The smaller plane continued to fly South into the Las Vegas and directly through the flight path of the eastbound air traffic that goes directly into the Airport.  The smaller plane then took a flight path towards the North Las Vegas Airport.
About 5 minutes later, a couple of Henderson pulled into the Von's loading dock area, which is in front of the dog park.
Like I said, I'm not sure what to make of this, but for a moment I thought I was about witness a mid air collision.