stupid to run onto the track, but other cars avoided Kevin easily, looks like TS gunned engine and wanted to spook/scare Kevin by passing close to him and swerving close to him, but overdid it a bit.
From what I can see,, and in MY opinion, he revved engine and served on purpose, and intentionally. Could have EASILY avoided even getting close to Kevin, just like all others did. I don't think wanted to KILL him, but he clearly INTENDED to spook him and get close to him - VERY CLEAR that he didn't want to slow down or get out of his way like others easily did.
...and too much of a coincidence that it was exactly TS's car that hit him, at which Kevin was yelling at (due to the incident in previous lap, where TS made Kevin's car get off course, which is supposedly a normal move in racing, but which made Kevin pretty angry and made him run out onto the track.)
Best video I could find as far as PQ goes:
http://deadspin.com/reports-tony-stewart-ran-over-opposing-driver-during-1618893708