News accounts say that Coolbaugh fell instantly after being struck in the head by a line drive off the bat of Tulsa's Tino Sanchez. The game between Arkansas and Tulsa was suspended immediately. Coolbaugh passed away less than an hour later.
Coolbaugh had played in the majors for the Brewers and Cardinals and his older brother Scott played in the majors as well.
People who have lived in Southern California have probably long heard Vin Scully going on about how base coaches should wear batting helmets. And a lot of us have thought Vin was just being something of an alarmist. I don't know if this tragedy will make it more likely for coaches to start wearing head protection, but perhaps the time has come. All minors who work on the field as a bat boys or ball boys are required to helmets. National high school rules require players who are serving as base coaches (which is fairly common) to wear helmets.
I think coaches are aware of the risk. Here is a photo I took last year of Cardinals third base coach Jose Oquendo when Albert Pujols Scott Rolen was at bat.