Tony Stewart won't face charges, a grand jury announced. (Getty Images)

An Ontario County, N.Y., grand jury cleared NASCAR's Tony Stewart of any charges on Wednesday afternoon stemming from the on-track death of Kevin Ward Jr. last month.

Approximately two dozen witnesses were heard, including other drivers, witnesses and medical experts, and the grand jury found "no basis to charge Tony Stewart with any crimes," Ontario County district attorney Michael Tantillo announced.

Tantillo also revealed, through toxicology evidence, that "at the time of operation, Kevin Ward was under the influence of marijuana." The levels of marijuana were enough to impair judgment, he said.

On top of witnesses, the grand jury investigation included two videos. One had been posted on YouTube while the other video was owned by the race track. Tantillo said that when enhanced and slowed down, both videos were relatively similar.

"The videos did not demonstrate any aberrational driving from Tony Stewart until the point of impact with Kevin Ward," he added.

Tantillo said that the grand jury deliberated for almost two days while considering the charges of manslaughter in the second degree and criminally negligent homicide. While the grand jury won't pursue charges against Stewart, there's still the possibility of a civil suit from Ward's family, who said the "matter is not at rest" in a statement.

"Our son got out of his car during caution while the race was suspended," said Pam Ward, Kevin's mother. "All the other vehicles were reducing speed and not accelerating, except for Tony Stewart, who intentionally tried to intimidate Kevin by accelerating and sliding his car towards him, causing the tragedy."

Findings from a preliminary investigation by the Ontario County (N.Y.) Sheriff's Department were disclosed to Tantillo, who then decided to present the case to a grand jury. Testimony and hearings were conducted this week.

"There were clearly different perceptions evidenced by different people on what they had seen and what they had heard. When you have that kind of different views of evidence, sometimes it's necessary to present a case to the grand jury to flesh out what the facts really are," Tantillo said. He declined to say whether any of the 23-member grand jury thought Stewart acted maliciously.

Stewart released a statement following Wednesday's announcement.

"This has been the toughest and most emotional experience in my life, and it will stay with me forever. ... I respect everything the DA and sheriff's office did to thoroughly investigate this tragic accident. While the process was long and emotionally difficult, it allowed for all the facts of the accident to be identified and known. 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." 

Ward was killed Aug. 9 after he was hit at Canandaigua Motorsports Park in upstate New York. Ward got out of his car and attempted to confront Stewart after Stewart had sent him into the wall on the prior lap. Stewart's back right tire clipped Ward and dragged him several feet.