While the deployment of National Guard troops and a curfew imposed in Baltimore is surely a factor, it is not the case that protests have stopped and people have left the streets—quite the opposite. Hundreds of people marched in Baltimore again on Wednesday, convening at City Hall. Leaders of these marches have made a concerted effort to make sure that they remain peaceful, and hope that large, calm marches can help to bring the focus back from the rioting to Freddie Gray and the larger question of police brutality in the city.

There are other signs of return to normal as well. Mayor Stephanie Rawlings-Blake says she's considering lifting the curfew—which runs from 10 p.m. to 5 a.m., through Tuesday— and sending the National Guard home early, citing the potential damage to businesses but necessarily acknowledging that the streets are basically calm. Meanwhile, half of the roughly 200 people arrested on Monday were released from jail. That's despite the fact that Governor Larry Hogan signed an order that allowed people to be held for longer than usual without charges. Police said they haven't had time to sift through the evidence and might file charges yet, and they insist the arrests were justified. (Kriston Capps notes here that, unusually, the Baltimore city jail is funded and run not by the city but by the state of Maryland.) But the fact that they're simply letting people out suggests that worries about violence breaking out again have subsided.

So why was Monday different? There are competing narratives, likely all with some truth. But with a few days' perspective, it looks like a combination of random chance and strategic errors by city authorities helped to create an explosive situation. First, there was the rumored "purge"—an idea circulating among high-school students, borrowing from the lawlessness in a fantasy movie of that name—to gather at Mondawmin Mall in West Baltimore and head toward the Inner Harbor. It seems there weren't even all that many students interested in a rowdy march—maybe 75 to 100.

But when they got to the mall, they were met by a phalanx of police in riot gear, which increased tensions. (It's also a departure from the general tactics of Baltimore Police over the last two weeks—officers have typically tried to give protestors a wide berth to demonstrate.) The mall is also a transportation hub for students, and many students of all ages who were not involved in the "purge" were therefore present in the same place and trying to get home. But police were forcing riders to get off buses and preventing them from getting on other buses and trains. The result was a large group of young people stranded together with no way to leave, facing off against a line of police, likely scared and unsure of what to expect. Unsurprisingly, the situation boiled over. Once police started backing off, some faction of the crowds took advantage of the anarchy and began setting fires and looting.