Gunmen have attacked the Canadian Parliament in Ottawa. One soldier guarding a war memorial has been killed, as has one assailant. Others may still be at large. The attack comes two days after Martin Rouleau-Couture, a radical Islamic convert, drove his car into two Canadian soldiers walking across a parking lot, killing one,

At this point, we have many more questions than answers.  Canadian officials have said that they are tracking some 90 suspected ISIS sympathizers in their country, and that Rouleou-Couture had been on that list. His passport had been seized prior to the attack on Monday to prevent travel to the Middle East. We have no idea yet whether today's attackers were linked to Rouleou-Couture, whether they were merely inspired by his actions, or whether the timing was coincidental.

Lone-wolf attacks such as that on Monday are almost impossible to predict or stop, particularly when the weapon involved is an automobile parked in a parking lot. In some ways, the ambush is reminiscent of the fatal attack last month on two Pennsylvania state troopers by a lone gunman, who is still at large.

One difference is of course Rouleou-Couture's professed conversion to Islam and identification with ISIS. But you also have to wonder whether the violence was caused by the conversion, or whether the conversion was itself a symptom of deeper problems. His friends and family have described him to the Canadian press as someone with emotional problems.

"Rouleau co-owned an industrial cleaning company that specialized in pressure washing the exteriors of buildings. About a year-and-a-half ago, Rouleau said his company had been robbed and he became enraged by his inability to get the authorities to take action against the culprit, according to the friend who asked not to be named.

"It was bizarre and extreme. He was surely depressed," said Jonathan Prince. "I think he was depressed and that's what led him to it. It was weird. He was normal one day and then changed the next."

Those who attacked Parliament today -- if indeed there were multiple attackers -- may prove to be another sort altogether. An organized, coordinated attack suggests a very real political message as opposed to a violent, personal lashing-out. It also highlights the inanity of obsessing over supposed threats coming into the country across our southern border with Mexico, when to the north we share the largest border in the world, almost all of it undefended and unguarded, and with a fairly large immigrant community.

Then again, Rouleau-Couture was born and raised in Quebec.