This appears to be the event of Sept 19, just being reported today:

United Airlines plane avoids near collision on descent to San Francisco; two passengers injured

According to the Federal Aviation Administration, one passenger was seriously injured and another suffered minor injuries last Thursday after pilots on UA flight 2428 from Newark, N.J., responded to a traffic collision avoidance system resolution advisory from the Oakland Air Route Traffic Control Center Airspace.

The Boeing 757-200 "slowed its descent to account for another aircraft at a lower altitude," United Airlines said in a statement. The maneuver is a "last defense against midair collisions," according to the National Business Aviation Association.

The incident last Thursday took place at 31,000 feet, about 70 miles north of San Francisco, according to FlightRadar24, which shows a Southwest Airlines flight about 3,000 feet below the United flight and a SkyWest flight about 1,000 feet lower.

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