Antitheft device kicks in while 2008 Hyundai Tucson is running

My Tucson 2008 model 2.0l ,while the car is running the anti theft device kicks in ,car performance is poor and the engine just stop. Please help

Why do you think it is the anti-theft? Is it Hyundai’s or an aftermarket unit?

When does the engine “just stop”? Is there a check engine light on? How many miles on this?