the Tribune has more complete information
http://www.chicagotribune.com/news/local/breaking/ct-met-man-shot-killed-chasing-bicyclist-hit-chatham-20180925-story.html
"The 39-year-old man was in a car, recording about 100 members of the Monday Night Ride group, when the blue SUV hit the woman around 1:30 a.m. in the Chatham neighborhood ....
The group meets late on Monday nights and ride about 15 miles through the city, picking a new route every week. Last week they were in the O’Hare-Belmont area. This week's route was through the South Side and there more people than usual turned out, Penro said.
He said usually the streets are quiet by the time the ride starts around 11 p.m. and lasts for about six hours. “It’s a pretty fun ride,” he said.
This Monday night the streets were a little busier than usual, he said. Penro remembered a man driving up to the group and tagging along, talking to some of the riders. He didn’t know who the man was, but believes he was the one who was shot.
Penro said he's been participating in the rides for nearly a year and has never felt unsafe.
The group was founded in 2013 and bills itself as an opportunity to explore neighborhoods."
The man shot was a cancer survivor. He doesn't seem to have been a member of the group or connected to the victim, just a Good Samaritan.