I think this is more about mental illness than anything else. The bicycle riders were on the sidewalk. This happened not too far from UH, just on the other side of i-45. I'm not familiar with that area, but it doesn't look that bad. And it was only 86° that day. It's not like it was 106°, heat which can have a heightened effect on the mentally unstable.
People who act out like this are already angry before they see someone on a bicycle. They take out there rage on who they believe poses no threat to them. Most of the time the perp doesn't make contact with there motor vehicle. Very few of these incidents are reported to the police, and very few of the reported incidents make the news. Texas appears to be solving some of these problems.