Selena Gomez -- SWATTED

7:10 PM PDT Law enforcement sources tell us Selena and her mom were home when officers arrived. They were both unaware of the 911 call, and had no idea why police were swarming the house.

Selena Gomez has just been swatted ... TMZ has learned.

It's the second time in 2 hours a celeb has been targeted. We broke the story ... Justin Timberlake was a swatting victim earlier this afternoon.

Law enforcement sources tell us ... the swatter called 911 and told the dispatcher ... her dad killed her mom with a gun that was among a cache of 20 weapons. The swatter then said the dad was going to burn the house down.