CANANDAIGUA, N.Y. (AP) — Prosecutors announced Wednesday that a grand jury had decided against bringing criminal charges against three-time NASCAR champion Tony Stewart in the August death of a driver at a sprint car race in upstate New York.

Ontario County District Attorney Michael Tantillo said the victim, Kevin Ward Jr., was under the influence of marijuana the night of the accident "enough to impair judgment." And he said two videos examined by investigators showed "no aberrational driving by Tony Stewart."

The decision came nearly seven weeks after Stewart's car struck and killed Ward during a dirt track race on Aug. 9. Stewart, the brash and popular NASCAR driver known as "Smoke," spent three weeks in seclusion following what he called a tragic accident before quietly returning to the Sprint Cup circuit. One of the biggest stars in the garage, Stewart has 48 career Cup wins in 542 starts but is winless this year and did not make the championship Chase field.

"This has been the toughest and most emotional experience of my life, and it will stay with me forever," Stewart said in a prepared statement. "While much of the attention has been on me, it's important to remember a young man lost his life. Kevin Ward Jr.'s family and friends will always be in my thoughts and prayers."

Tantillo could have determined the case on his own but last week said he would take it to a grand jury. Experts said it would have been difficult to prove criminal intent, but the prosecutor asked the grand jury to consider charges of second-degree manslaughter and criminally negligent homicide.

"There were not 12 votes to either charge," he said.

A call placed to the Ward family's home went unanswered.

Sheriff Philip Povero spent weeks investigating, several times saying investigators did not have evidence to suggest Stewart meant to harm the other driver at the track in tiny Canandaigua. Ward had spun while racing alongside Stewart and then the 20-year-old climbed out of his car and walked down the track, waving his arms in an apparent attempt to confront the 43-year-old NASCAR veteran.

Authorities said the first car to pass Ward had to swerve to miss hitting him. The front of Stewart's car appeared to clear Ward, but Ward was struck by the right rear tire and hurtled through the air. He died of blunt force trauma and his father later told a newspaper there was "no reason" for the death given Stewart's skills and experience.

The sheriff asked in the days after Ward's death for spectators to turn over photos and videos of the crash as investigators worked to reconstruct the accident. Among the things being looked at were the dim lighting, how muddy it was and whether Ward's dark firesuit played a role in his death, given the conditions.

A fan's video was widely circulated after Ward's death, but details of the second video obtained by the sheriff have not been made public.

Stewart, who Povero described as "visibly shaken" after Ward's death, vowed to cooperate in the investigation but he did not testify before the grand jury. He issued a brief statement expressing deep sadness and then dropped off the radar, missing races at Watkins Glen, Michigan and Bristol before coming back for the Aug. 31 race at Atlanta.

Looking far different then the fiery driver his fans love, Stewart quietly read a statement at a news conference in which he said the death of a driver he hit was "one of the toughest tragedies I've ever had to deal with."

"This is something that will definitely affect my life forever," Stewart said then. "This is a sadness and a pain I hope no one has to experience in their life. That being said, I know that the pain and mourning that Kevin Ward's family and friends are experiencing is something that I can't possibly imagine."

Stewart's peers were protective of him as questions emerged in the aftermath of the crash, and it pained them that Stewart was grieving in private and had cut off communication with so many of them. They welcomed him back in Atlanta, and fans gave him a robust cheer, too. Two days later during the race, his No. 14 Chevrolet slammed into the wall twice and Stewart settled for a dismal 41st-place finish.

After Ward's death, NASCAR announced a rule that prohibits drivers from climbing out of a crashed or disabled vehicle — unless it is on fire — until safety personnel arrive. The series also cleared the way for Stewart to make its Chase for the Sprint Cup championship with a win, despite missing the three races.