Video of the crash showed Ward, in the No. 13 car, spin into a wall after contact with Stewart's car. The video showed Ward climb quickly from his car and briskly walk around it in what appeared to be an attempt to confront Stewart as he passed by in his own car, Stewart's familiar No. 14.
The video showed Ward to the right of Stewart's car, which seemed to kick out from the rear and hit Ward. The driver was hurtled through the air and emergency personnel quickly reached Ward as he lay on the track.
Dale Earnhardt Jr. tweeted his condolences to Ward's family on Sunday morning.
We will all loose someone in our time. When a loss is sudden and unexpected, the pain & sadness is suffocating. Prayers for the Ward family.- Dale Earnhardt Jr. (@DaleJr) August 10, 2014
The accident came just four days after the one-year anniversary of an accident in a sprint car race in Iowa in which Stewart suffered a compound fracture to his right leg. The injury cost him the second half of the NASCAR season.
The track, about 30 miles southeast of Rochester, canceled the remainder of Saturday's race within five minutes and later posted a message on its Facebook page encouraging fans to "pray for the entire racing community of fans, drivers, and families."
Stewart was involved in a July 2013 accident at Canandaigua Motorsports Park that seriously injured a 19-year-old driver. He later took responsibility for his car making contact with another and triggering the 15-car accident that left Alysha Ruggles with a compression fracture in her back.
Stewart only returned to sprint track racing last month, almost a year after breaking his leg in the crash in Iowa. He didn't return to racing in any form until February, when preparation for NASCAR's season-opening Daytona 500 began.
He refused to stop his extracurricular racing despite the injury. The multimillionaire is known to participate in races with purses worth less than $3,000 and drive alongside drivers of varying ages and talent levels.
Stewart was a spectator at the Knoxville Nationals in Iowa on Tuesday, the one-year anniversary of the accident, and posted on his Twitter account: "Thank you to everyone that worked so hard to get me back to where I'm at today. It's your life, live it!"
Even though he will not race Sunday, Stewart can still make the Chase if he wins before the Chase. Including Sunday, there are five races before the Chase (Watkins Glen, Michigan, Bristol, Atlanta, Richmond).
The new Chase rules state that a driver must attempt to qualify for all 26 races before the Chase (unless they are given an injury exemption). Stewart qualified his car, but since he won't start the race, he won't receive any points.
ESPN.com's Brant James, ESPN Stats & Information and The Associated Press contributed to this report.