Tesla had (has?) many defects in their batteries and they were putting dangerous units into production cars when they should have been thrown away. They were also hiding the defects in the financial accounting by marking them as test units instead of scrap.

Tripp tried to bring the issue to management's attention. Musk and management ignored him. Tripp then went to the press. Musk then fired him, put him under 24/7 surveillance, tapped his cell phone using a stinger, and seemingly[1] ordered someone to "SWAT" him by calling in a fake threat that Tripp was armed and coming to Tesla to "shoot up the place". Tripp is now suing.

[1] Hard to believe that it wasn't done a Musk's direction given that similar things have happened to other whisteblowers (child services was called on another [I believe she is now suing], Musk personally called the boss of at least one other, Musk tried to get another external whistleblower arrested by falsely claiming vehicular assault [and also tried to get him expelled], that person is now suing).