Drug overdoses took a deadly toll in Santa Rosa over the weekend. Police are investigating the deaths of four young people, and the hospitalization of two more, to see if they are connected to a man arrested for selling narcotics,

Their sudden passing has prompted an outpouring of grief and raised urgent concerns about the dangers of fentanyl-laced drugs. As investigators work to piece together what happened, here’s what we know so far.

A stabbing in a classroom at a high school in Santa Rosa sent the school in lockdown after one student turned a knife on another. One student was arrested and the other had to undergo surgery for their injuries,