... In the meantime,
If there is a microSD card in the blackberry, remove it. Also go ahead and remove the SIM card for now. Replace the battery after waiting a minute or two. See what happens. If it boots up, remove the batter again and replace the SIM card and see what happens. If all is well, then try with the microSD card.
If still no joy, take a look at: How do I wipe the BlackBerry using Jl Cmder? - BlackBerryFAQ
and What to do next if Jl Cmder will not connect and wipe - BlackBerryFAQ
Wipe with JL_CMDER and then install the OS.