Federal officials said Tuesday they are investigating the actions of a U.S. Marshals Service employee who was caught on video grabbing a woman’s cell phone in South Gate, smashing it to the ground and kicking it away. The video, which was filmed by another woman across the street from the police activity, was posted on YouTube. It shows a woman using her cell phone to record a law enforcement operation, and a Marshals Service employee approaches her, grabs the phone and slams it on the ground. “On (Sunday), a YouTube video entitled ‘South Gate Police Attack Cop Watcher: Destroys Cellphone’...