I've been mucking around with Infuse for awhile and rooted my phone; changed kernels and Roms a few times. I don't recognize that symptom.
I will say that based on reading the xda Infuse forums, the Infuse is almost unbrickable. 98% of the time when the phone appears "bricked", it is not hard-bricked, just soft-bricked. That means there are things to do to fix it usually just by hooking to a computer. It requires someone that knows what they're doing, or you may be able to do it yourself if you post the question at xda Infuse forums (or here, but there's not as much expert traffic in the Infuse forum here as there is in the xda Infuse forum) and work at understanding the responses.
You might want to post full details of what your son did. What tool did he use to root? Did he succeed at rooting and then try to flash a ROM?
Most often on xda with problem like this, the first thing suggested is to try Odin or Heimdall (if you can get to download mode). I've used Heimdall to flash qkster's back-to-stock GB 2.3.6. package. Heimdall can be finicky.. requires trying several times with different computer, different cord, remove/reinstall drivers, read xda instructions very closely. In a word - persistence.
I have my phone lost once for 1 day and once for 4 days, trying to work similar problem (boot loop in my case). The 4-day adventure was sort of a nightmare... took me 4 days at probably 4-5 hours per day to get Heimdall to work. It started on a Monday, couldn't do anything during y 12-hour work days, had to work at night, and desperately needed the phone before a big family trip planned for the weekend. I was a sleep-deprived wreck by Thursday, but I got it working.
What I wish I had done instead (*) was to mosey on down to Walmart and buy a $100 AT&T phone like Fusion. Then I could move my SIM into the cheap phone and use it while I fixed my Infuse at my leisure. After it's fixed and SIM goes back into the Infuse and the cheap Fusion goes into the desk drawer... but it's still not wasted money... that cheap phone will always be there if you need it as a backup for anything breaking on your infuse (or any AT&T phone in your house). For example if battery completley dies and becomes non-rechargeable.... you can get a new one but it's going to take you a week or two. If you send it off to someone for repair, that'll take awhile. There's always more options and less pressure if you have time.
(*) - I'm pretty sure this will work. Not 100% but 95%. You might poke around a little more to double check if you take this advice to buy a cheap AT&T phone while you repair your infuse.