According to witnesses, Siddoway's vehicle continued along North Temple and struck a Nissan Versa that was stopped westbound at the traffic light at 400 West. It then continued through the intersection where it collided with a red Saturn that was stopped eastbound at the light.
Kunz, a passenger in the Versa, later died from injuries suffered in the crash, charging documents show.
Prosecutors allege that Siddoway had been involved in a number of previous crashes due to his seizures and knew he shouldn't have been driving when his truck struck the car Kunz was riding in.
The seizures, which allegedly cause Siddoway to lose motor control and be unresponsive for minutes at a time, started in 2009, charging documents show.
Siddoway told investigators that the "episodes" occurred anywhere from monthly to every six months, even while on medication, according to charging documents.
On Feb. 19, 2011, Siddoway allegedly had a seizure while driving his Ford F-150 in Coalville. During that incident he drove off the roadway and crashed into a driveway of a nearby home, charging documents show. Siddoway then fled before police could arrive.
In April 2011, Siddoway suffered a seizure that lasted 10 minutes at restaurant.
In May 2011, he was driving in Provo Canyon in his F-150 when he suffered another seizure, prosecutors allege. When he regained consciousness, the Ford was tangled up in cables in the median.
Then in May 2011, he suffered a seizure while on medication in which he was incoherent for about 40 minutes. He told his doctor that the "smaller seizures are happening every several days," charging documents state.
But he also told the doctor he was doing well on his medication and was "not interested in further evaluation."
After Siddoway suffered seizures in July, August and September 2011, his doctor told him not to drive until he had been seizure-free for at least two months.
In November 2011, Siddoway allegedly submitted a form to the driver's license division claiming his last seizure was in July 2011, prosecutors allege.
In October 2012, Siddoway had another seizure. When he saw his doctor, Siddoway admitted he continued "to experience 'auras' without seizures once a month," which concerned the doctor enough to increase the seizure medication.
But neither Siddoway nor the doctor reported the incidents to the driver license division, prosecutors said.
Siddoway is scheduled to make his initial court appearance Thursday in 3rd District Court.