That was the early speculation based on a report from a Pakistani newspaper they picked up. There had been a bomb threat tied to the trial.
Its looking now more likely that this was a known criminal acting alone. How he got a Kalashnikov and grenades (that may turn out to be flash-bangs) is unknown.
Attacker in Liége confirmed 31 year-old Moroccan-Belgian with criminal background in drug and weapons charges
A jihadi cannot have a criminal record and still be a jihadi? To make a case for it being a "criminal acting alone", you must supply at least a plausible criminal motive for the attack.
In the absence of such a motive, the only motive that remains is a jihad response to yesterday's honor killing convictions.