NO GOOGLING - - - uWu - - - RIDDLE

Once there lived a happy couple. (Husband & Wife)
The husband went to work as always. And the wife went shopping.
On her way, 2 cars pulled up. And shot her in the head. Killing her. T^T
The police arrived immediately. -
After arriving at the crime scene, the police contacted her husband.
And said his wife has been found dead.
A few minutes later... the husband showed up.
And the police arrested him immediately. -
Why?